Preparation method of shale layered polymer, sheet-like ultra-microporous carbonaceous adsorbent and its preparation method and hydrogen isotope separation application

Abstract

The present invention discloses a preparation method of a shale layered polymer, a sheet-like ultra-microporous carbonaceous adsorbent, its preparation method, and hydrogen isotope separation application. The preparation method of the shale layered polymer comprises sequentially adding hydroquinone, p-phenylenediamine, and terephthalaldehyde to N,N-dimethylformamide in a molar ratio of (0-1):1:2 and dissolving them, wherein the molar ratio of p-phenylenediamine to N,N-dimethylformamide is 1:20-1:200; polymerizing the above solution, and vacuum drying to obtain a writable polymer. The sheet-like ultra-microporous carbonaceous adsorbent is a monolithic microporous carbon obtained by carbonizing a shale layered polymer precursor, and has slit-type ultra-micropores with pore diameters concentrated in the range of 0.40-0.47 nm. In a 77K hydrogen and deuterium static adsorption test, the sheet-like carbonaceous adsorbent with optimized pore structure can achieve a deuterium adsorption amount higher than that of hydrogen. In the dynamic low-temperature penetration experiment, the separation of hydrogen and deuterium was also successfully achieved; in addition, the sheet-like ultra-microporous carbon adsorbent can also achieve the adsorption separation of ethane and ethylene.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical gas separation, and specifically discloses a method for preparing a shale layered polymer, a flaky ultra-microporous carbonaceous adsorbent, and its preparation and hydrogen isotope separation application. Background Art

[0002] Due to environmental pollution and related climate change issues, as well as the depletion of fossil fuels, the demand for clean energy is increasing. Controlled nuclear fusion energy is considered the ultimate clean energy source due to its inherent safety, pollution-free advantages, and abundant fuel resources. However, these fusion reactors require hydrogen isotopes as fuel, so the stable production of deuterium (D), an important hydrogen isotope in nuclear fusion reactions, is crucial to this process. In addition, deuterium is also very important in scientific and technological fields and industry, such as neutron scattering methods, non-radioactive isotope tracing, and neutron moderators in nuclear reactors. However, the abundance of deuterium on Earth is very low, only 0.0156%. In addition, the molecular size (0.29nm), shape, and chemical properties of H2 and D2 are very similar, making separation of the two very difficult.

[0003] Currently, the main methods for enriching D2 include electrolysis, distillation, chemical exchange, cryogenic distillation, and thermal diffusion. However, these hydrogen isotope separation methods often suffer from drawbacks such as high energy consumption, equipment requirements, and high costs. Compared to these separation techniques, low-temperature adsorption separation based on quantum effects is a promising approach for hydrogen isotope separation due to its low energy consumption and simple process. At low temperatures, the adsorption of isotopic gas molecules within micropores produces quantum effects, amplifying differences in gas adsorption behavior. The de Broglie wavelengths of H2 and D2 at 77 K are 0.18 and 0.11 nm, respectively, indicating that the actual sizes of H2 and D2 during adsorption separation on nanoporous materials are 0.47 (0.29 + 0.18 nm) and 0.40 (0.29 + 0.11 nm), respectively. Therefore, constructing adsorbents with ultra-micropores of 0.40–0.47 nm is crucial for achieving adsorption separation of the two.

[0004] Currently, the ultra-microporous adsorbents commonly used for H2 / D2 separation mainly include metal-organic frameworks, zeolites, and porous carbon materials. Among them, porous carbon adsorbents are very promising due to their advantages such as simple preparation, high specific surface area, adjustable pore structure and surface chemistry, and stable structure. For example, biomass such as ginkgo leaves and peanut shells are used as carbon precursors to prepare ultra-microporous carbon materials for hydrogen isotope separation. However, due to the complex structure of the biomass precursor, its micropore size is large and the distribution is not concentrated, resulting in poor H2 / D2 separation performance (Micro.Meso.Mater., 2020, 304, 109291.). In addition, under dynamic separation conditions, effective adsorption separation is only observed in the initial stage or under zero coverage (under low pressure). In addition to experimental studies, calculation results also show that the equilibrium selectivity of hydrogen isotope mixtures reaches its maximum at zero coverage and decreases as smaller pores are filled. The above findings indicate that increasing the accessible ultra-small pore entrances in the adsorbent will be an effective way to enhance kinetic H2 / D2 separation. According to previously studied separation strategies, compared to common porous carbon adsorbents, sheet-like carbon nanosheets can provide shorter diffusion paths and more easily access ultramicropores (Nano Lett., 2022, 22, 6615-6621.). Given the increased number of accessible ultramicropores in sheet-like adsorbents, hydrogen isotope selectivity at zero coverage is expected to improve. Therefore, the development of carbon nanosheet materials with a high density of accessible ultramicropores for efficient H2 / D2 adsorption separation is of great significance. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing shale layered polymers, a sheet-like ultra-microporous carbonaceous adsorbent and a preparation method thereof, and to use the sheet-like ultra-microporous carbonaceous adsorbent to achieve low-temperature adsorption separation of hydrogen and deuterium and separation of ethane and ethylene.

[0006] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing shale layered polymers comprises the following steps:

[0008] S1: hydroquinone, p-phenylenediamine, and terephthalaldehyde are sequentially added to N,N-dimethylformamide (DMF) in a molar ratio of (0-1):1:2 and fully dissolved, wherein the molar ratio of p-phenylenediamine to DMF is 1:20-1:200;

[0009] S2: pouring the above solution into a reactor for polymerization, and vacuum drying to obtain the shale layered polymer.

[0010] The molar ratio of the hydroquinone, p-phenylenediamine and terephthalaldehyde is (0.2-1):1:2.

[0011] The polymerization temperature is 0-150° C., and the polymerization time is 0.5-12 hours; further, the polymerization temperature is 20-120° C., and the polymerization time is 2-8 hours.

[0012] The vacuum drying temperature is 0-150° C., and the vacuum drying time is 2-96 hours; further, the vacuum drying temperature is 20-130° C., and the vacuum drying time is 5-80 hours.

[0013] The present invention also provides a sheet-like ultra-microporous carbon adsorbent, which has a sheet-like microscopic morphology and has slit-type microporous channels with pore diameters concentratedly distributed in the range of 0.40 to 0.47 nm.

[0014] The present invention also provides a method for preparing the flaky ultra-microporous carbonaceous adsorbent, which comprises carbonizing the shale layered polymer at high temperature under an inert atmosphere to obtain the flaky ultra-microporous carbonaceous adsorbent.

[0015] Furthermore, when the molar ratio of hydroquinone, p-phenylenediamine and terephthalaldehyde is (0.2-1):1:2, the micropore size distribution of the sheet-like ultra-microporous carbon adsorbent is more concentrated in the range of 0.40-0.44 nm.

[0016] The carbonization process is carried out at room temperature for 2 to 10 min. -1 Heat to 200-600℃ and hold for 1-4h, then heat for 2-10min -1 Raise the temperature to 700-1200℃ and stay for 2-4h.

[0017] The present invention also provides an application of the flaky ultra-microporous carbonaceous adsorbent in hydrogen isotope separation, wherein the flaky ultra-microporous carbonaceous adsorbent is used for H2 / D2 separation.

[0018] H2 / D2 separation is a low-temperature adsorption separation process, the volume ratio of H2 and D2 is (0.1~99.9):(99.9~0.1), the adsorption temperature is -197~-100℃ (77~173K), and the adsorption pressure is 0.1~20bar; further, the volume ratio of H2 and D2 is (1~99):(99~1), and the adsorption pressure is 0.5-18bar.

[0019] The present invention also provides an application of the sheet-like ultra-microporous carbon adsorbent in ethylene / ethane separation.

[0020] The present invention also provides a method for regenerating the sheet-like microporous carbon adsorbent, wherein after the separation is completed (H2 / D2 or ethylene / ethane separation is completed), the adsorbent is regenerated at 25-300°C in a 5-30 mL min -1 The product can be reused after purging with inert gas at a flow rate of 1-4 hours.

[0021] The beneficial effects of the present invention are as follows:

[0022] The obtained shale layered polymer has a writable function; the flaky ultra-microporous carbonaceous adsorbent is obtained by controlling the synthetic raw material ratio, synthesis conditions and carbonization temperature of the shale layered polymer precursor, thereby changing the structure of the ultra-micropores of the final flaky carbonaceous adsorbent, so that it has slit-type channels mainly with a diameter of 0.40 to 0.47 nm, which can selectively adsorb D2, thereby realizing low-temperature adsorption separation of H2 / D2; in addition, the flaky ultra-microporous carbonaceous adsorbent can also realize the adsorption separation of ethane and ethylene.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] 1. The shale layered polymer of the present invention is graffiti-able.

[0025] 2. The sheet-like ultra-microporous carbon adsorbent of the present invention has ultra-micropores of 0.40-0.47 nm, and can improve the separation performance of hydrogen isotopes compared to ordinary carbon adsorbents.

[0026] 3. The synthesis method of the sheet-like ultra-microporous carbonaceous adsorbent of the present invention is relatively simple, and the conditions during the precursor synthesis process are mild. The obtained carbonaceous adsorbent has a monolithic macroscopic morphology, and can be quickly and large-scale synthesized into carbonaceous adsorbent particles of various macroscopic shapes for low-temperature adsorption and separation of hydrogen isotopes.

[0027] 4. The sheet-like ultra-microporous carbon adsorbent prepared by the method of the present invention can not only be used for low-temperature adsorption separation of hydrogen isotopes, but can also be used as a multi-purpose carbon adsorbent for adsorption separation of ethylene and ethane. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Optical photograph (a) and electron microscope image (b) of the polymer precursor of Example 1.

[0029] Figure 2 The polymer atomic force topography image (a) and the corresponding height information map (b) of Example 1.

[0030] Figure 3 This is an optical picture of the writing font of the monolithic polymer rod in Example 1.

[0031] Figure 4 This is an electron microscope image of the flaky carbonaceous adsorbent of Example 1.

[0032] Figure 5 N2 physical adsorption-desorption isotherms of the adsorbents of Example 1 and Example 2 at 77K.

[0033] Figure 6 1 and 2 are water vapor physical adsorption-desorption isotherms of the adsorbents of Example 1 and Example 2 at 298K.

[0034] Figure 7 The C2H4 / C2H6 adsorption-desorption isotherms of the adsorbents of Example 1(a) and Example 2(b) at 298K.

[0035] Figure 8 The adsorbent of Example 2 was subjected to a total flow rate of 4 mL min at 298 K, 1 bar, and C2H4 / C2H6 (50:50). -1 The penetration curve.

[0036] Figure 9 H2 / D2 physical adsorption-desorption isotherms of the adsorbents of Example 1(a) and Example 2(b) at 298K.

[0037] Figure 10 For Example 1(a) and Example 2(b), at 298K, 1 bar, H2 / D2 / Ne (1:1:8) with a total flow rate of 10 mL min -1 The penetration curve. Specific embodiments

[0038] The technical solution of the present invention is further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0039] ①Material synthesis

[0040] Weigh hydroquinone, p-phenylenediamine, and terephthalaldehyde in a molar ratio of (0-1):1:2 and add them to DMF to fully dissolve them. Then pour the solution into the reactor for polymerization. Then take out the sample and dry it in vacuum at 100℃ for 48 hours to obtain a monolithic shale layered polymer ( Figure 1 ).

[0041] The shale layered polymer obtained according to the above preparation method was heated at room temperature for 5 ℃ min under inert gas. -1 The temperature was raised to 200°C and held for 5 hours. The temperature was then further raised to 700-1200°C for carbonization to obtain a sheet-like ultra-microporous carbon adsorbent. The experimental conditions and pore sizes for each example are shown in Table 1. The prepared sheet-like carbon adsorbent was subjected to ethylene and ethane adsorption and desorption isotherms. The shapes of the ethylene and ethane isotherms were observed, and the pore size of the carbon adsorbent was determined based on the molecular sizes of ethylene and ethane.

[0042] The structures of the shale layered polymer and flaky carbonaceous adsorbent prepared in Example 1 and Example 2 were characterized:

[0043] Depend on Figure 1 It can be seen from a that since it is a liquid phase synthesis method, the precursor can be directly reacted in the mold to obtain a monolithic polymer. The polymer was further characterized by scanning electron microscopy (SEM). Figure 1 As can be seen from b, the polymer is formed by the gradual accumulation of many thin sheets, and its shape is similar to shale, so the polymer is named shale layered polymer. In order to clarify the thickness of the single layer polymer, atomic force microscopy (AFM) was used to characterize it. Figure 2 a is the AFM picture of the polymer sample, which shows that the sample is in the form of flakes. Figure 2 b further shows that the thickness of a single layer of polymer sample is only 4-6nm. In addition, the polymer is a monolithic structure and is stacked by ultra-thin nanosheets, so it has the function of being smearable, such as Figure 3 The monolithic polymer rod shown can be used as a "crayon" to achieve writing function. After high temperature carbonization of shale layered polymer, a sheet-like carbonaceous adsorbent can be obtained. Figure 4 It can be seen that the microstructure of the carbon adsorbent is mainly a flake structure, and the flake surface is relatively rough.

[0044] To investigate the effect of varying the amount of hydroquinone used during precursor synthesis on the microporous structure of the material, we selected a polymer-derived sheet-like carbonaceous adsorbent (Example 1) without hydroquinone added during synthesis and a polymer-derived sheet-like carbonaceous adsorbent (Example 2) with hydroquinone added. We first characterized the results using N2 adsorption-desorption tests. Figure 5 It can be seen that Example 2 does not adsorb N2, while Example 1 adsorbs N2 but has difficulty desorbing it, indicating that the large size of N2 molecules cannot diffuse well into the micropores of the adsorbent at 77K. Further pore structure testing of the sample was conducted using water molecules with a smaller molecular size (0.26nm). Figure 6 It can be seen that both have high water vapor adsorption capacity, and the water vapor adsorption capacity of Example 1 and Example 2 reaches 8.4 and 6.7 mmol g respectively. -1 , indicating that both samples have a very rich microporous structure. The water vapor adsorption of Example 2 is lower than that of Example 1. Combined with the N2 adsorption results, this indicates that the addition of hydroquinone during the synthesis process can reduce the microporous structure of the final carbon material. To clarify the pore structure size of the material, ethylene ethane was used as a molecular probe. Figure 7 It is the ethylene-ethane adsorption isotherm of the material and it can be seen from the figure that both Example 1 and Example 2 can achieve the separation of ethylene-ethane. Figure 7 It can be seen from a that Example 1 has difficulty in desorbing ethane, indicating that the narrow slit-type carbon pores have a strong restriction on ethane. Therefore, the micropore size of Example 1 is close to the kinetic size of ethane molecules, 0.45 nm. Figure 7b It can be seen that Example 2 has difficulty in desorbing ethylene, indicating that the narrow slit-type carbon pores have a strong restriction on ethylene. Therefore, the ultra-micropore size of Example 2 is close to the kinetic size of ethylene molecules, 0.42nm. The material of Example 2 was further subjected to a dynamic penetration test of ethylene and ethane at 298K and 1 bar. Figure 8 It can be seen that since Example 2 does not adsorb ethane at all, ethane breaks through the adsorption column instantly. In contrast, ethylene is adsorbed in the adsorption column for a longer time and only breaks through the adsorption column 20 minutes after ethane breaks through. This shows that Example 2 can also achieve good separation in the ethylene and ethane mixed gas separation experiment.

[0045] Table 1 Preparation conditions and micropore diameters of carbonaceous adsorbents in various examples

[0046]

[0047]

[0048] ②Material testing

[0049] Ideal Static Adsorption Test: 50 ± 2 mg of flaky carbonaceous adsorbent was weighed and loaded into the sample tube of a Micromeritics ASAP 2020 physical adsorption instrument and degassed at 200°C for 24 hours. The sample tube was then placed in a Dewar flask filled with -197°C liquid nitrogen. High-purity H2 or D2 gas was introduced into the sample tube and the gas adsorption capacity at different equilibrium pressures was measured to generate adsorption isotherms for different isotopes.

[0050] Low-temperature dynamic penetration test: Under adsorption conditions of -197°C and 1 bar, a uniform 1:1 mixture of high-purity H₂ and high-purity D₂ was introduced into the adsorption column, along with high-purity Ne as a distribution gas. The resulting mixture consisted of H₂, D₂, and Ne in a 1:1:8 ratio. This mixture was then passed through an adsorption column containing a flaky carbon adsorbent that had been degassed at 200°C for 24 hours. The adsorption column measured 150 mm by 80 mm and was connected to an online gas mass spectrometer at its outlet to monitor the gas composition. The adsorption capacity and separation time were then calculated. Specific performance is shown in Table 2.

[0051] Specifically, the hydrogen isotope low-temperature adsorption separation performance data of the flaky carbonaceous adsorbents of Examples 1 and 2 are as follows:

[0052] Depend on Figure 9 It can be seen that the adsorption capacity of H2 and D2 in Example 1 at 100 kPa is 5.5 mmol g -1 , the H2 / D2 ideal gas selectivity (IAST) selectivity is 1.2. Figure 9b It can be seen that the adsorption capacity of H2 and D2 in Example 2, in which hydroquinone was introduced during the synthesis of the precursor, was 4.63 mmol g at 100 kPa. -1 and 4.87 mmol g -1 The IAST selectivity of H2 / D2 is 1.9, which proves that the pore size can be adjusted by adjusting the hydroquinone content to improve the separation performance of hydrogen isotopes. Figure 10 (a) It can be seen that the co-adsorption time of H2 and D2 in implementation 1 is as long as 60 minutes, and the separation time is 3 minutes. Figure 10 (b) It can be seen that the co-adsorption time of H2 and D2 in Example 2 is only 13 minutes, and the separation time can reach 5 minutes, showing good H2 / D2 separation performance.

[0053] Table 2 Low-temperature adsorption performance of hydrogen isotopes of flaky carbonaceous adsorbents

[0054]

[0055]

Claims

1. A sheet-like microporous carbon adsorbent, characterized in that: The invention relates to a slit-shaped ultra-microporous channel having a pore size concentratedly distributed between 0.40 nm and 0.47 nm; the shale layered polymer is carbonized at high temperature under an inert atmosphere to obtain a sheet-like ultra-microporous carbonaceous adsorbent; and the preparation method of the shale layered polymer comprises the following steps: S1. Hydroquinone, p-phenylenediamine, and terephthalaldehyde are sequentially added to N,N-dimethylformamide in a molar ratio of (0-1):1:2 and fully dissolved. The molar ratio of p-phenylenediamine to N,N-dimethylformamide is 1:20-1:

200. S2: Pour the above solution into a reactor for polymerization, and vacuum dry it to obtain a shale layered polymer.

2. The sheet-like microporous carbon adsorbent according to claim 1, characterized in that: The molar ratio of the hydroquinone, p-phenylenediamine and terephthalaldehyde is (0.2-1):1:

2.

3. The sheet-like microporous carbon adsorbent according to claim 1, characterized in that: The polymerization temperature is 0-150° C., and the polymerization time is 0.5-12 h.

4. The sheet-like ultra-microporous carbon adsorbent according to claim 1, characterized in that: The carbonization temperature is 700~1200 o C.

5. Use of the sheet-like microporous carbon adsorbent according to claim 1 in hydrogen isotope separation, characterized in that: The flaky ultra-microporous carbon adsorbent is used for H2 / D2 adsorption separation.

6. Use of the sheet-like ultra-microporous carbon adsorbent according to claim 1 in ethylene / ethane separation.

7. A method for regenerating the sheet-like microporous carbon adsorbent according to claim 1, characterized in that: After separation is completed, o 5-30 mL min at C -1 The inert gas was purged for 1-4 h.

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