A multi-level porous carbon material and applications thereof
By using ZIF-based derived hierarchical porous carbon materials and high-temperature activation, the problem of separating octafluoropropane in existing technologies has been solved. This method achieves efficient and stable separation of hexafluoropropylene and octafluoropropane, meeting electronic-grade purity requirements, and the preparation process is environmentally friendly and pollution-free.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHEJIANG UNIV
- Filing Date
- 2022-10-17
- Publication Date
- 2026-05-19
AI Technical Summary
Existing technologies for separating and purifying octafluoropropane suffer from problems such as unstable reaction, low yield, numerous byproducts, high separation difficulty, high cost, and low adsorbent selectivity, making it difficult to meet the requirements for electronic-grade purity.
ZIF-derived hierarchical porous carbon materials were used as adsorbents. Through high-temperature activation, hierarchical porous carbon materials with microporous-mesoporous structures and uniform pore size distribution were prepared for the adsorption and separation of hexafluoropropylene and octafluoropropane, taking advantage of their high adsorption capacity and selectivity.
It achieves efficient and stable separation of hexafluoropropylene and octafluoropropane, with high adsorption capacity and strong selectivity. It is suitable for separation under low temperature conditions, meets the requirements of electronic grade purity, and the preparation process is environmentally friendly and pollution-free.
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Figure CN117902574B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of adsorption separation, specifically relating to a hierarchical porous carbon material and its application in the adsorption separation of hexafluoropropylene and octafluoropropane. Technical Background
[0002] Octafluoropropane, also known as perfluoropropane, is a halogenated hydrocarbon with excellent chemical and thermal stability. It has attracted considerable attention due to its non-toxic, odorless, highly stable, thermally conductive, electrically insulating, and physiologically resistant properties. Currently, octafluoropropane is widely used in industries such as microelectronics, medicine, and cryogenic refrigeration. Particularly in semiconductor manufacturing, its demand has been increasing year by year due to the accelerated pace of domestic chip research and industrial production in my country in recent years. Furthermore, as chip manufacturing process dimensions decrease, the purity requirements for octafluoropropane are becoming increasingly stringent.
[0003] Existing literature reports that the synthetic routes for octafluoropropane include direct gas-phase fluorination of hydrocarbons, fluorination of chlorofluorocarbons, pyrolysis of fluorinated hydrocarbons, electrolytic fluorination in hydrogen fluoride, and fluorination addition of hexafluoropropene. Among these, direct gas-phase fluorination of hydrocarbons is particularly problematic due to its vigorous reaction, releasing a large amount of heat, which easily leads to the breaking of carbon bonds and the formation of numerous dimers and polymers, resulting in low yields. Fluorination of chlorofluorocarbons and pyrolysis of fluorinated hydrocarbons also yield octafluoropropane in very low amounts with numerous byproducts, making industrial production difficult. Electrolytic fluorination in hydrogen fluoride exhibits low reaction selectivity and produces complex product compositions, increasing the difficulty of separating and purifying octafluoropropane.
[0004] Currently, the main purification methods for octafluoropropane include cryogenic distillation, adsorption separation, catalytic conversion, and membrane separation. Cryogenic distillation is the most widely used and mature method, but it involves the removal of trace impurities, especially azeotropic and near-azeotropic impurities, which must be brought to the electronic grade. This inevitably leads to a sharp increase in the theoretical number of distillation columns, increasing both cost and operational difficulty.
[0005] Catalytic conversion transforms impurities with similar boiling points to the target product into impurities with significantly different boiling points through chemical conversion. This method is only effective for certain impurities and is prone to side reactions that reduce yield. Current membrane separation methods are only suitable for separating substances with significantly different molecular sizes from octafluoropropane, such as N2 and He, and the separation purity is limited. Compared to distillation, adsorption separation is simpler to operate, has lower operating costs, and the adsorbent is easily recoverable, making it an environmentally friendly green separation technology. Currently, widely used adsorbent materials include molecular sieves, activated carbon, and carbon molecular sieves. However, these adsorbents have low adsorption capacity and selectivity for different impurities; often, a single adsorbent material can only specifically adsorb one type or class of impurities, making it difficult to find a universally applicable adsorbent material. Summary of the Invention
[0006] The purpose of this invention is to provide a hierarchical porous carbon material derived from a zeolite-like imidazole ester (ZIF) framework and its application in the adsorption and separation of hexafluoropropylene and octafluoropropane. The ZIF-based hierarchical porous carbon material provided by this invention has good stability, abundant and suitable pore size distribution, and high adsorption capacity and high adsorption and separation selectivity when applied to the adsorption and separation of hexafluoropropylene and octafluoropropane.
[0007] In a first aspect, the present invention provides a hierarchical porous carbon material, comprising a ZIF-based derived hierarchical porous carbon material obtained by heat treatment of a ZIF-based material, wherein the ZIF-based derived hierarchical porous carbon material has micropores with a pore size of 0.5-2 nm.
[0008] In some embodiments, the microporosity of the ZIF-based derived hierarchical porous carbon material is 50-95%, for example, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or any value between therewith. In some preferred embodiments, the microporosity of the ZIF-based derived hierarchical porous carbon material is 70-90%. Here, microporosity refers to the ratio of the volume occupied by micropores in the porous body to the total volume of the porous body.
[0009] The ZIF-based derived hierarchical porous carbon material of the present invention has a microporous-mesoporous hierarchical pore structure and a uniform and effective pore size distribution, with the pore size mainly distributed in the range of 0.5-2.0 nm, for example, mainly distributed in the range of 0.5-2.0 nm, 0.6-2.0 nm, 0.6-1.0 nm or 0.5-0.8 nm, where "mainly" means at least 50% of the pore size.
[0010] In some embodiments, the specific surface area of the ZIF-based derived hierarchical porous carbon material is 200-1000 m². 2 / g, for example, 200m 2 / g、300m 2 / g、400m 2 / g、600m 2 / g、800m 2 / g, 1000m 2 / g or any value between them. In some preferred embodiments, the specific surface area of the ZIF-based derived hierarchical porous carbon material is 300-800 m². 2 / g.
[0011] In some embodiments, the micropore specific surface area of the ZIF-based derived hierarchical porous carbon material is 100-800 m². 2 / g, for example, 100m 2 / g、200m 2 / g、400m 2 / g、600m 2 / g、800m 2 / g or any value between them. In some preferred embodiments, the microporous specific surface area of the ZIF-based derived hierarchical porous carbon material is 200-700 m². 2 / g. In this invention, the microporous specific surface area refers to the specific surface area of the micropores in the ZIF-based derived hierarchical porous carbon material, and the specific surface area refers to the total specific surface area of the ZIF-based derived hierarchical porous carbon material. Both are measured by low-temperature nitrogen adsorption-desorption experiments, but the specific methods used are different.
[0012] In some embodiments, the total pore volume of the ZIF-based derived hierarchical porous carbon material is 0.1-0.5 cm³. 3 / g, for example, 0.1cm 3 / g, 0.2cm 3 / g, 0.3cm 3 / g, 0.4cm 3 / g, 0.5cm 3 / g or any value between them. In some preferred embodiments, the total pore volume of the ZIF-based derived hierarchical porous carbon material is 0.25-0.4 cm³. 3 / g.
[0013] In some embodiments, the micropore volume of the ZIF-based derived hierarchical porous carbon material is 0.05-0.4 cm³. 3 / g, for example, 0.05cm 3 / g, 0.1cm 3 / g, 0.2cm 3 / g, 0.3cm 3 / g, 0.4cm 3 / g or any value between them. In some preferred embodiments, the micropore volume of the ZIF-based derived hierarchical porous carbon material is 0.1-0.3 cm³. 3 / g.
[0014] In some embodiments, the ZIF-based material includes at least one of ZIF-67, ZIF-7, ZIF-8, or ZIF-11.
[0015] In some embodiments, the heat treatment temperature is 500-1000°C, for example 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C or any value between them.
[0016] In some embodiments, the heat treatment time is 0-10 hours, for example, 1 hour, 2 hours, 4 hours, 6 hours, 8 hours, 10 hours or any value between them.
[0017] In some embodiments, the heat treatment includes activating the ZIF-based material at a high temperature by first heating it to 500-800°C at a heating rate of 1-10°C / min in an inert gas atmosphere, and then heating it to 600-1000°C at a heating rate of 1-10°C / min.
[0018] In some embodiments, the heat treatment includes high-temperature activation of the ZIF-based material in an inert gas atmosphere by first raising the temperature to 500°C at a heating rate of 1-10°C / min, and then raising the temperature to 600-800°C at a heating rate of 1-10°C / min.
[0019] In some embodiments, the heat treatment includes high-temperature activation of the ZIF-based material by raising the temperature to 700-800°C at a heating rate of 8-10°C / min and maintaining it for 0-8 hours in an inert gas atmosphere.
[0020] In some embodiments, the inert gas includes at least one of nitrogen, helium, or argon. In some embodiments, the flow rate of the inert gas is 10-200 mL / min, for example, 10 mL / min, 50 mL / min, 100 mL / min, 150 mL / min, 200 mL / min, or any value between them.
[0021] In some embodiments, the method further includes degassing the heat-treated ZIF-based material. Preferably, the degassing process includes vacuum degassing at 100-200°C for 5-20 hours.
[0022] In some embodiments, the ZIF-based derived hierarchical porous carbon material has a shape including at least one of spherical, powdery, columnar, granular, or film-like forms.
[0023] In some embodiments, ZIF-67 is used as the raw material, and high-temperature activation is performed in an inert gas atmosphere by heating to 800°C at a rate of 10°C / min and maintaining the temperature for 8 hours, resulting in a microporosity of 85.6% and a specific surface area of 329.37 m². 2 / g, ZIF-67-based derived carbon materials with pore sizes of 0.5-2.0 nm.
[0024] In some embodiments, ZIF-7 is used as the raw material, and high-temperature activation is performed in an inert gas atmosphere by heating to 800°C at a rate of 10°C / min and maintaining the temperature for 8 hours, resulting in a microporosity of 83.6% and a specific surface area of 756.22 m². 2 / g, ZIF-7-based derived carbon materials with pore sizes of 0.6-1.0 nm.
[0025] In some embodiments, ZIF-8 is used as the raw material, and high-temperature activation is performed in an inert gas atmosphere by raising the temperature to 800°C at a rate of 10°C / min and maintaining it for 8 hours, resulting in a microporosity of 66.4% and a specific surface area of 853.59 m². 2 / g, ZIF-8-based derived carbon materials with pore sizes of 0.6-2.0 nm.
[0026] In some embodiments, ZIF-11 is used as the raw material, and high-temperature activation is performed in an inert gas atmosphere by heating to 800°C at a rate of 10°C / min and maintaining the temperature for 8 hours, resulting in a specific surface area of 494.3 m². 2 ZIF-11-based derived carbon materials with a density of / g, a microporosity of 76.1%, and a pore size of 0.5-0.8nm.
[0027] In some embodiments, the ZIFs-based carbon material can be commercially available. In other embodiments, the ZIFs-based carbon material can also be prepared by at least one of the following methods:
[0028] (1) Synthesis method of ZIF-67: Cobalt nitrate hexahydrate and 2-methylimidazole are dissolved in methanol and stirred thoroughly. The mixture is stirred at room temperature for 24 h, centrifuged, washed, and vacuum dried to obtain ZIF-67 crystals; preferably, the molar ratio of cobalt nitrate hexahydrate, 2-methylimidazole and methanol is 1:(3-4):(200-400), preferably 1:3.75:(200-400);
[0029] (2) Synthesis method of ZIF-7: Dissolve benzimidazole in ethanol. Then, add ammonia to the benzimidazole / ethanol solution, stir at room temperature, and then add zinc acetate dihydrate. Stir the mixture at room temperature for 3 hours, centrifuge, wash, and vacuum dry to obtain ZIF-7 crystals; preferably, the molar ratio of zinc acetate dihydrate, benzimidazole, ammonia and ethanol is 1:(1-3):(1-3):(200-400), preferably 1:2:2:(200-400);
[0030] (3) Synthesis method of ZIF-8: Zinc nitrate hexahydrate and 2-methylimidazole are dissolved in methanol and stirred thoroughly. The mixture is stirred at room temperature for 24 h, centrifuged, washed, and vacuum dried to obtain ZIF-8 crystals; preferably, the molar ratio of zinc nitrate hexahydrate, 2-methylimidazole and methanol is 1:(3-4):(200-400).
[0031] (4) Synthesis method of ZIF-11: Dissolve benzimidazole in ethanol. Then, add toluene and ammonia to the benzimidazole / ethanol solution, stir at room temperature, and then add zinc acetate dihydrate. Stir the mixture at room temperature for 3 hours, centrifuge, wash, and vacuum dry to obtain ZIF-11 crystals; preferably, the molar ratio of zinc acetate dihydrate, benzimidazole, ammonia, toluene and ethanol is 1:(1-3):(1-3):(80-120):(200-400), preferably 1:2:2:100:(200-400).
[0032] In some embodiments, the centrifugation conditions in (1), (2), (3) and (4) above include: 6000-10000 rpm for 5-15 minutes.
[0033] In some embodiments, the washing in (1), (2), (3) and (4) above includes washing with methanol or ethanol 2-3 times.
[0034] In some embodiments, the drying temperature in (1), (2), (3) and (4) above is 50-60°C and the vacuum degree is -0.1 to -0.08 MPa.
[0035] In this paper, ZIF-based materials, namely zeolite-like imidazole ester framework materials, are zeolite-like MOF materials synthesized by reacting Zn(I) or Co(II) with imidazole ligands. Compared with zeolite molecular sieves, ZIF materials possess a richer pore structure, including some topologies not found in zeolite molecular sieves. By coordinating metal ions with different organic ligands, ZIF materials with different structural properties can be formed, and replacing the metal ions in the material can derive ZIF materials with the same topology but different properties.
[0036] This invention uses ZIF-based materials as raw materials and performs high-temperature activation in an inert gas atmosphere to obtain ZIFs-derived hierarchical porous carbon materials. The ZIFs-derived hierarchical porous carbon materials prepared by the above method exhibit stable structural properties and regular particle shape when used as adsorbents, demonstrating high selectivity and adsorption capacity in the adsorption and separation of hexafluoropropylene and octafluoropropane.
[0037] In a second aspect, the present invention provides a method for separating hexafluoropropylene and octafluoropropane, comprising separating a mixed gas containing hexafluoropropylene and octafluoropropane by adsorption with an adsorbent comprising the hierarchical porous carbon material described in the first aspect.
[0038] In some embodiments, the adsorption separation temperature is 15-50°C, for example 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 55°C, 50°C or any value between them.
[0039] In some embodiments, the total pressure of the mixture is 10-1000 kPa, for example, 10 kPa, 20 kPa, 50 kPa, 100 kPa, 200 kPa, 400 kPa, 600 kPa, 800 kPa, 1000 kPa or any value between them.
[0040] The carbon material used in the method of this invention for separating hexafluoropropylene and octafluoropropane has a uniform and effective pore size distribution and a microporous-mesoporous hierarchical pore structure, and also has high adsorption capacity and high selectivity. The saturated adsorption capacity of hexafluoropropylene reaches 1.2-4.5 mmol / g, and the IAST selectivity at a hexafluoropropylene / octafluoropropane mixing ratio of 1 / 99 reaches 6-541. This hierarchical porous carbon material can be used for pressure swing adsorption of hexafluoropropylene and octafluoropropane, and it still has good separation performance, especially under low pressure conditions, which meets the requirements for further purification of octafluoropropane to the electronic grade.
[0041] Compared with the prior art, the present invention has the following advantages:
[0042] (1) The zeolite-like imidazole ester framework material used in the preparation of ZIF-based derived carbon materials involved in this invention can be synthesized on a large scale, has stable properties, and has mild synthesis conditions.
[0043] (2) The ZIF-based derived carbon material preparation method involved in this invention is simple, does not require the addition of additional chemical pore-forming agents, and is environmentally friendly.
[0044] (3) The hierarchical porous carbon material involved in this invention has a stable structure and performance, high adsorption capacity for hexafluoropropylene, high adsorption selectivity for C3F6 / C3F8, and good regeneration cycle performance, maintaining the original adsorption level after multiple adsorption-regeneration cycles. Its performance in the adsorption and separation of hexafluoropropylene and octafluoropropane is far superior to most adsorbent materials. Attached Figure Description
[0045] Figure 1 The adsorption isotherms of hexafluoropropylene and octafluoropropane on the ZIF-67-based derived carbon material prepared in Example 1 are shown.
[0046] Figure 2 The adsorption isotherms of hexafluoropropylene and octafluoropropane on the ZIF-7-based derived carbon material prepared in Example 2 are shown.
[0047] Figure 3 The adsorption isotherms of hexafluoropropylene and octafluoropropane on the ZIF-8-based derived carbon material prepared in Example 3 are shown.
[0048] Figure 4 The adsorption isotherms of hexafluoropropylene and octafluoropropane on the ZIF-11-based derived carbon material prepared in Example 4 are shown.
[0049] Figure 5 The image shows the low-temperature nitrogen adsorption-desorption curve of the ZIF-11-based derived carbon material prepared in Example 4.
[0050] Figure 6 The image shows the fixed-bed breakthrough curve of the ZIF-11-based derived carbon material prepared in Example 4 to a mixture of hexafluoropropylene and octafluoropropane.
[0051] Figure 7 This is a pore size distribution diagram of the ZIF-11-based derived carbon material prepared in Example 4. Detailed Implementation
[0052] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.
[0053] Example 1
[0054] 2g of ZIF-67 was weighed into a ceramic boat, which was then placed in a high-temperature tube furnace. High-purity nitrogen was used as the protective gas, with a flow rate of 25 mL / min. The temperature was increased to 800℃ at a rate of 10℃ / min and maintained at this temperature for 8 hours. The material was then naturally cooled to room temperature to obtain ZIF-67-derived hierarchical porous carbon material. The ZIF-67-derived hierarchical porous carbon material was then degassed under vacuum at 150℃ for 12 hours, followed by low-temperature nitrogen adsorption-desorption experiments.
[0055] The ZIF-67-derived microporous carbon material prepared in this embodiment has a microporosity of 85.6% and a specific surface area of 329.37 m². 2 / g, microporous specific surface area is 281.86 m² 2 / g, with the main pore size distribution concentrated in 0.5-2.0 nm.
[0056] To test the adsorption and separation performance of the ZIF-67-derived hierarchical porous carbon material prepared in this embodiment, single-component static adsorption experiments were conducted using the ZIF-67-derived hierarchical porous carbon material as the adsorbent for hexafluoropropylene and octafluoropropane gases, respectively. 100 mg of adsorbent was used, and the adsorption temperature was set to 25°C. Figure 1 As shown, the results indicate that at 25 °C and 1 bar, the adsorption capacity of hexafluoropropylene reaches 1.29 mmol / g, while the adsorption capacity of octafluoropropane is 1.01 mmol / g. Calculating the IAST selectivity, at a C3F6 / C3F8 volume ratio of 1:99, the adsorption selectivity of this adsorbent for the two gases reaches 1.08 at 1 bar.
[0057] Example 2
[0058] 2g of ZIF-7 was weighed into a ceramic boat, which was then placed in a high-temperature tube furnace. High-purity nitrogen was used as the protective gas, with a flow rate of 25 mL / min. The temperature was increased to 800℃ at a rate of 10℃ / min and maintained at this temperature for 8 hours. The material was then naturally cooled to room temperature to obtain ZIF-7-derived hierarchical porous carbon material. The ZIF-7-derived hierarchical porous carbon material was then degassed under vacuum at 150℃ for 12 hours, followed by low-temperature nitrogen adsorption-desorption experiments.
[0059] The ZIF-7-derived hierarchical porous carbon material prepared in this embodiment has a microporosity of 83.6% and a specific surface area of 756.22 m². 2 / g, microporous specific surface area is 631.99 m² 2 / g, with the main pore size distribution concentrated in 0.6-1.0 nm.
[0060] To test the adsorption and separation performance of the ZIF-7-derived hierarchical porous carbon material prepared in this embodiment, single-component static adsorption experiments were conducted using the ZIF-7-derived hierarchical porous carbon material as the adsorbent for hexafluoropropylene and octafluoropropane gases, respectively. 100 mg of adsorbent was used, and the adsorption temperature was set to 25°C. Figure 2 As shown, the results indicate that at 25 °C and 1 bar, the adsorption capacity of hexafluoropropylene reaches 2.47 mmol / g, while the adsorption capacity of octafluoropropane is 0.85 mmol / g. Calculating the IAST selectivity, at a C3F6 / C3F8 volume ratio of 1:99, the adsorption selectivity of this adsorbent for the two gases at 1 bar reaches 537.6.
[0061] Example 3
[0062] 2g of ZIF-8 was weighed into a ceramic boat, which was then placed in a high-temperature tube furnace. High-purity nitrogen was used as the protective gas, with a flow rate of 25 mL / min. The temperature was increased to 800℃ at a rate of 10℃ / min and maintained at this temperature for 8 hours. The material was then naturally cooled to room temperature to obtain ZIF-8-derived hierarchical porous carbon material. The ZIF-8-derived hierarchical porous carbon material was then degassed under vacuum at 150℃ for 12 hours, followed by low-temperature nitrogen adsorption-desorption experiments.
[0063] The ZIF-8 derived hierarchical porous carbon material prepared in this embodiment has a microporosity of 66.4% and a specific surface area of 853.5905 m². 2 / g, microporous specific surface area is 566.79 m² 2 / g, with the main pore size distribution concentrated in 0.6-2.0 nm.
[0064] To test the adsorption and separation performance of the ZIF-8-derived hierarchical porous carbon material prepared in this embodiment, single-component static adsorption experiments were conducted using the ZIF-8-derived hierarchical porous carbon material as the adsorbent for hexafluoropropylene and octafluoropropane gases, respectively. 100 mg of adsorbent was used, and the adsorption temperature was set to 25°C. Figure 3 As shown, the results indicate that at 25 °C and 1 bar, the adsorption capacity of hexafluoropropylene reaches 3.96 mmol / g, while the adsorption capacity of octafluoropropane is 2.70 mmol / g. Calculating the IAST selectivity, at a C3F6 / C3F8 volume ratio of 1:99, the adsorption selectivity of this adsorbent for the two gases reaches 8.1 at 1 bar.
[0065] Example 4
[0066] 2g of ZIF-11 was weighed into a porcelain boat, which was then placed in a high-temperature tube furnace. High-purity nitrogen was used as the protective gas, with a flow rate of 25 mL / min. The temperature was increased to 800℃ at a rate of 10℃ / min and maintained at this temperature for 8 hours. The material was then naturally cooled to room temperature to obtain ZIF-11-derived hierarchical porous carbon material. This ZIF-11-derived hierarchical porous carbon material was then degassed under vacuum at 150℃ for 12 hours, followed by a low-temperature nitrogen adsorption-desorption experiment. The results are as follows: Figure 5 As shown, within the low-pressure range, the adsorption capacity increases sharply with increasing pressure, exhibiting a typical Type I curve, indicating that the ZIF-11-derived hierarchical porous carbon material possesses a microporous structure. Furthermore, the adsorption-desorption curve shows a distinct hysteresis loop with increasing pressure, suggesting that the ZIF-11-derived hierarchical porous carbon material also possesses a mesoporous structure. Therefore, this ZIF-11-derived hierarchical porous carbon material is a hierarchical porous material with multiple pore structures, including micropores and mesopores.
[0067] The ZIF-11-derived hierarchical porous carbon material prepared in this embodiment has a microporosity of 76.1% and a specific surface area of 494.30 m². 2 / g, microporous specific surface area is 376.22 m² 2 / g, such as Figure 7 As shown, the results indicate that the main effective pore size distribution of the material is concentrated in the range of 0.5–0.8 nm, with a total pore volume of 0.2161 cm³. 3 / g, micropore volume is 0.1843 cm³ 3 / g.
[0068] To test the adsorption and separation performance of the ZIF-11-derived hierarchical porous carbon material prepared in this embodiment, single-component static adsorption experiments were conducted using the ZIF-11-derived hierarchical porous carbon material as the adsorbent for hexafluoropropylene and octafluoropropane gases, respectively. 100 mg of adsorbent was used, and the adsorption temperature was set to 25°C. Figure 4As shown, the results indicate that at 25 °C and 1 bar, the adsorption capacity of hexafluoropropylene reaches 2.36 mmol / g, while the adsorption capacity of octafluoropropane is 0.72 mmol / g. Calculating the IAST selectivity, at a C3F6 / C3F8 volume ratio of 1:99, the adsorption selectivity of this adsorbent for the two gases at 1 bar reaches 541.4.
[0069] To test the actual performance of the ZIF-11-derived hierarchical porous carbon material prepared in this embodiment for separating a mixture of hexafluoropropylene and octafluoropropane, a fixed-bed breakthrough experiment was conducted using the synthesized hierarchical porous carbon material as an adsorbent. In this embodiment, the gas mixture of hexafluoropropylene and octafluoropropane was adsorbed and separated at a volume ratio of 1:99, with a breakthrough temperature of 25°C and a pressure of 0.1 MPa. The test results are as follows: Figure 6 As shown, when the volume ratio of hexafluoropropylene to octafluoropropane is 1:99 and the mixed gas flow rate is 1.8 mL / min, octafluoropropane begins to permeate from 5 minutes, while hexafluoropropylene only begins to permeate from 335 minutes. Theoretically, a single adsorption can obtain 1207 bed volumes of high-purity octafluoropropane (product purity >99.9999%), with a product yield of 98.5%.
[0070] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of this application.
Claims
1. A method for separating hexafluoropropylene and octafluoropropane, comprising adsorbing and separating a mixed gas containing hexafluoropropylene and octafluoropropane using an adsorbent, wherein the adsorbent comprises a hierarchical porous carbon material, wherein the hierarchical porous carbon material comprises a ZIF-derived hierarchical porous carbon material obtained by heat treatment of a ZIF-based material, the ZIF-derived hierarchical porous carbon material having micropores with a pore size of 0.5-2 nm.
2. The method according to claim 1, characterized in that, The microporosity of the ZIF-based derived hierarchical porous carbon material is 50-95%.
3. The method according to claim 2, characterized in that, The microporosity of the ZIF-based derived hierarchical porous carbon material is 70-90%.
4. The method according to claim 1, characterized in that, The ZIF-based derived hierarchical porous carbon material has one or more of the following characteristics: (a) The specific surface area of the ZIF-based derived hierarchical porous carbon material is 200-1000 m². 2 / g; (b) The micropore specific surface area of the ZIF-based derived hierarchical porous carbon material is 100-800 m². 2 / g; (c) The total pore volume of the ZIF-based derived hierarchical porous carbon material is 0.1-0.5 cm³. 3 / g; (d) The micropore volume of the ZIF-based derived hierarchical porous carbon material is 0.05-0.4 cm³. 3 / g.
5. The method according to claim 4, characterized in that, The ZIF-based derived hierarchical porous carbon material has one or more of the following characteristics: (a) The specific surface area of the ZIF-based derived hierarchical porous carbon material is 300-800 m². 2 / g; (b) The micropore specific surface area of the ZIF-based derived hierarchical porous carbon material is 200-700 m². 2 / g; (c) The total pore volume of the ZIF-based derived hierarchical porous carbon material is 0.25-0.4 cm³. 3 / g; (d) The micropore volume of the ZIF-based derived hierarchical porous carbon material is 0.1-0.3 cm³. 3 / g.
6. The method according to any one of claims 1-5, characterized in that, The ZIF-based material includes at least one of ZIF-67, ZIF-7, ZIF-8, or ZIF-11.
7. The method according to any one of claims 1-5, characterized in that, The heat treatment temperature is 500-1000℃, and the heat treatment time is 1-10h.
8. The method according to any one of claims 1-5, characterized in that, The heat treatment temperature is 700-900℃, and the heat treatment time is 5-10h.
9. The method according to any one of claims 1-5, characterized in that, The heat treatment temperature is 700-800℃, and the heat treatment time is 8-10h.
10. The method according to claim 9, characterized in that, The shape of the ZIF-based derived hierarchical porous carbon material includes at least one of spherical, powdery, columnar, granular, or film-like forms.
11. The method according to any one of claims 1-5, characterized in that, The adsorption separation temperature is 15-50℃, and the total pressure of the mixed gas is 10-1000kPa.