Application of surface-modified carbon adsorbents in simulated moving bed separation of light isotopes

Abstract

This invention provides the application of surface-tuned carbon adsorbents in the separation of light isotopes in a simulated moving bed, belonging to the field of light isotope gas separation technology. The surface-tuned carbon adsorbent has a hierarchical porous structure, tunable surface chemistry, a nitrogen content of 2-26 at.%, and surface polarity exhibiting a water vapor adsorption capacity of 0.1-4.4 mmol / g at a relative humidity of 10%. The micropore size of the carbon adsorbent is centered at 4.1 Å. The hierarchical porous structure and surface-rich heteroatom characteristics of this adsorbent promote the diffusion and selective recognition of light isotopes, while also exhibiting a short mass transfer time. When used in a simulated moving bed for the separation of light isotopes, it demonstrates excellent separation performance and regeneration efficiency. Using a D2 / H2 mixture as the separation target, the D2 concentration in the recovered gas reaches 85.0%, and regeneration is completed in 15 minutes. Furthermore, a 1% D2 concentration mixture can be concentrated to 20%, achieving a D2 recovery rate of 90%.

Description

Technical Field

[0001] This invention belongs to the field of light isotope gas separation technology, and relates to the application of a surface-controlled carbon adsorbent in the separation of light isotopes in a simulated moving bed. Background Technology

[0002] hydrogen( 2 H), carbon ( 13 C) Nitrogen 15 N), oxygen ( 18 Light isotopes such as oxygen (O) are indispensable in key fields such as isotope tracing, nuclear magnetic resonance (NMR), and biomedicine. However, the physicochemical properties of light isotopes are extremely similar, making their separation a highly challenging technical problem. Traditional techniques for light isotope separation mainly include chemical exchange processes and cryogenic distillation. These methods generally suffer from high energy consumption and low separation efficiency, resulting in high overall separation costs. Low-temperature adsorption methods based on adsorption separation technology are typically implemented in fixed-bed systems, resulting in long non-adsorption cycles, low production efficiency, and low throughput per unit time.

[0003] Simulated moving bed (SMB) is a separation device that utilizes the principle of adsorption. As a major representative of continuous separation equipment, it boasts advantages such as high production efficiency and automated continuous production, and is widely used in the separation of natural products, petrochemicals, and chiral compounds. SMB is a complex industrial process involving numerous influencing factors; it is a nonlinear, non-equilibrium, non-ideal, and multi-degree-of-freedom periodic process. SMB divides a fixed bed into multiple adsorption bed segments with separation capabilities. The opening and closing of solenoid valves, which can be autonomously programmed, divides these segments into adsorption, regeneration, and displacement zones. SMB utilizes multi-channel solenoid valve combination control, switching between these channels to achieve periodic process switching, thereby achieving the separation of products.

[0004] The inherent shortcomings of existing light isotope separation technologies necessitate the development of new, highly efficient separation technologies. Summary of the Invention

[0005] The separation of light isotopes using SMB technology at liquid nitrogen temperature (or higher operating temperature) is a novel and efficient technique for continuous separation of light isotopes. This also places higher demands on the preparation of adsorbents. For carbon adsorbents, the inert surface of conventional carbon adsorbents makes it difficult to identify differences between light isotopes, while porous carbon adsorbents obtained by controlling pore size have a long mass transfer zone, which is detrimental to the application of SMB. Based on this, this invention controls the chemical environment of porous carbon with a hierarchical pore structure, thereby reducing the length of the adsorbent mass transfer zone and enhancing the selective recognition of light isotopes by the adsorbent at the operating temperature. For the technology of separating light isotopes using SMB, taking D2 / H2 mixed gas as the separation target, under the operating temperature, the purity of D2 in the D2 / H2 mixed gas can be increased to 85.0%, and regeneration can be completed in 15 minutes; at the same time, in a D2 / H2 mixed gas with 1% D2 purity, the purity of D2 in the D2 / H2 mixed gas can be increased to 20%, and the D2 recovery rate reaches 90%.

[0006] The technical solution of the present invention is as follows: Application of a surface-modified carbon adsorbent in the separation of light isotopes using a simulated moving bed, comprising the following steps: S1 The adsorption column is filled with pre-activated carbon adsorbent, and the pipeline and adsorbent are purged with inert gas to remove impurity gases. S2 Immerse the adsorption column and corresponding gas pipeline in a coolant at a constant temperature of 77-160 K until the temperature is constant; during this process, close the outlet valve of the adsorption column and continuously introduce inert gas into the adsorption column to maintain the pressure inside the column at a positive pressure to prevent impurity gases from entering. S3. Light isotope feed gas is introduced into at least two adsorption columns performing adsorption, displacement gas is introduced into at least two adsorption columns performing displacement, and at least two adsorption columns performing regeneration are regenerated. S4 operates for 1-15 minutes each time, switching valves to perform different operations on the adsorption columns to simulate the adsorbent moving in the opposite direction to the gas. After the valve is switched, the first adsorption column that was performing adsorption performs a displacement operation, the first adsorption column that was performing displacement performs a regeneration operation, the first adsorption column that was performing regeneration performs an adsorption operation, and the remaining adsorption columns simulate moving in the same direction. Specifically, the Xth adsorption column performs the operation originally performed by the X-1th adsorption column (X≥2), and the first adsorption column performs the operation originally performed by the last adsorption column. The carbon adsorbent has a hierarchical porous structure with tunable surface chemistry. The nitrogen content is 2-26 at.%, and the surface polarity is such that the water vapor adsorption capacity is 0.1-4.4 mmol / g at a relative humidity of 10%. The micropore size of the carbon adsorbent is distributed around 4.1 Å. The light isotope feed gas includes hydrogen isotopes, oxygen isotopes, methane isotopes, nitrogen isotopes, ammonia isotopes, carbon dioxide isotopes, or rare gas isotopes, and the replacement gas in the same operation includes heavy component isotopes.

[0007] The hydrogen isotopes include H2 / D2, D2 / T2, H2 / T2, or H2 / D2 / T2; the oxygen isotopes include... 16 O2 / 18 O2, the methane isotopes include 12 CH4 / 13 CH4 or 12 CH4 / 12 CD 4； Nitrogen isotopes include 14 N2 / 15 N2; ammonia isotopes include 14 NH3 / 15 NH3 or 14 NH3 / 14 ND3; the carbon dioxide isotopes include 12 CO2 / 13 CO2 or 12 C 16 O2 / 12 C 18 O2; the rare gas isotopes include 3 He / 4 He 20 Ne / 21 Ne / 22 Ne or 36 Ar / 38 Ar / 40 Ar.

[0008] The carbon adsorbent has a nitrogen content of 12-26 at.% and exhibits surface polarity, with a water vapor adsorption capacity of 2.2-4.4 mmol / g at a relative humidity of 10%.

[0009] The BET surface area of ​​the carbon adsorbent is 238-560 m². 2 g -1 The micropore volume is 0.07-0.21 cm³. 3 g -1 .

[0010] The carbon adsorbent particles have a size of 0.1 mm to 2 mm.

[0011] In step S3, the adsorption columns are arranged from right to left according to the operation sequence as the adsorption zone, the displacement zone, and the regeneration zone, with the adsorption column numbers decreasing sequentially.

[0012] The adsorption column for performing adsorption is connected in series with the adsorption column for performing displacement; at least two adsorption columns for performing displacement perform multi-stage displacement to further enrich the heavy components; the light component and heavy component mixed gas flowing out from the top of the adsorption column for performing displacement enter the adsorption column for performing adsorption to further recover the heavy components.

[0013] The adsorption columns that perform regeneration are connected in parallel to increase regeneration efficiency.

[0014] The adsorption columns that perform adsorption are connected in series; the adsorption columns that perform displacement are connected in series.

[0015] The regeneration includes one or more of purging, vacuum, and vacuum purging.

[0016] Step S4 also includes collecting and / or detecting the product after running 5-10 rounds.

[0017] The carbon adsorbent is obtained by pyrolysis of a porous carbon precursor polymer formed by a substitution reaction of monomers and linking units (which serve as the linking units of the monomers); the monomers include one or more of cyanuric chloride, melamine, p-phenylenediamine, hydrazine and its dihydrazine compounds, m-phenylenediamine, and ethylenediamine; the linking units include one or more of piperazine, dichloro-p-xylene, terephthaloyl chloride, isophthaloyl chloride, terephthalaldehyde, and glutaraldehyde.

[0018] The method for preparing the porous carbon precursor polymer specifically includes the following steps: S01 Dissolve the monomer and the linking unit in 50-250 mL of organic solvent to obtain a homogeneous organic solution. At 20-30℃ and a stirring rate of 300-700 rpm / min, slowly pour the organic solution containing the linking unit into the organic solution containing the monomer to obtain a milky white organic emulsion containing the prepolymer. SO2 acid-binding agent is added dropwise to a milky white organic emulsion containing prepolymer at a rate of 1-10 mL / sec; the mixture is heated to 40-80 °C at a speed of 300-700 rpm / min and held for 3-12 h to obtain a porous carbon precursor polymer.

[0019] The molar ratio of the monomer to the connecting unit is 1-3.5 : 0.5-5.5.

[0020] The molar ratio of the acid-binding agent to the monomer is 1.5-4.5.

[0021] The acid-binding agent includes one or more of triethylamine, N,N-diisopropylethylamine, 4-dimethylaminopyridine, ammonia, methylamine, and ethylenediamine.

[0022] The organic solvent includes tetrahydrofuran, methanol, ethanol, or N,N-dimethylformamide.

[0023] A thermal environment of 40-80 ℃ is provided by oil bath, ultrasound or microwave.

[0024] The pyrolysis conditions are as follows: inert gas flow rate of 30-200 mL / min, heating rate of 2-5 ℃ / min, pyrolysis temperature of 500-900 ℃, and pyrolysis time of 1-4 h.

[0025] Pre-activation in step S1 includes high-temperature vacuum degassing.

[0026] The degassing temperature is 150-300 ℃, the vacuum degree is 0.05-1 torr, and the degassing time is 6-24 h.

[0027] The inlet flow rate of the light isotope feed gas and the displacement gas is 5-200 mL / min.

[0028] The pressure in the adsorption column is 0.1-2 bar.

[0029] The simulated moving bed includes an isotope gas control system, a solenoid valve, a cryogenic control system, an integrated control system, and an adsorption column; The isotope gas control system includes isotope gas, flow controller and gas mixing pipeline. The isotope gas is connected to the flow controller and then to the gas mixing pipeline. The gas mixing pipeline is connected to the adsorption column. The solenoid valves include several solenoid valves placed at the top, bottom and sides of the adsorption column tower; The cryogenic control system includes a cold trap, a liquid level controller, and a mechanical transmission device; a coolant is added to the cold trap to keep the temperature of the adsorption column and corresponding pipeline constant at 77 K-160 K; the mechanical transmission device is a scissor lift to immerse or remove the adsorption column and corresponding gas pipeline from the cold trap. The integrated control system includes control software running on a computer and a PLC controller. The computer is connected to the PLC controller via a network cable, and the PLC controller is connected to a flow controller and a solenoid valve via a network cable to control the flow rate of isotope gas, the flow of gas into the adsorption column in the gas mixing pipeline, the flow of product gas out of the adsorption column, and the series or parallel connection mode between adsorption columns.

[0030] The gas in the gas mixing pipeline includes a light isotope feed gas and a displacement gas. The light isotope feed gas is connected to the adsorption column for adsorption, and the displacement gas is connected to the adsorption column for displacement.

[0031] The coolant includes liquid nitrogen or a mixture of liquid nitrogen and an organic solvent.

[0032] The organic solvent includes one or more of isopentane, n-pentane, diethyl ether, ethanol, methanol, acetone, hexane, n-butanol, ethyl acetate, and propylamine.

[0033] The liquid level controller is connected to the cold trap via a coolant pipeline and automatically replenishes coolant to maintain a constant liquid level.

[0034] It also includes a product collection system, which includes a gas storage tank connected to the top of the adsorption column or connected to the bottom of the adsorption column via a vacuum pump.

[0035] It also includes a product detection system, which includes a mass spectrometer connected to the top of the adsorption column or to the bottom of the column via a vacuum pump.

[0036] The beneficial effects of this invention are: This invention obtains a carbon adsorbent with high nitrogen content, high polarity, and a hierarchical porous structure by controlling the surface chemistry of the carbon adsorbent. The hierarchical pore size distribution of the polar porous carbon endows it with low mass transfer resistance and short equilibrium time when separating light isotopes. Therefore, this polar porous carbon exhibits macroscopic characteristics such as a short mass transfer time in the single-column breakthrough curve and high selectivity for the separation of light isotope mixtures when separating light isotopes. Using a simulated moving bed (SMB) for light isotope separation, it has excellent separation performance and regeneration efficiency. Taking D2 / H2 separation as an example, the purity of D2 obtained reaches 85%, and regeneration can be completed in only 15 minutes. In a low-temperature continuous D2 enrichment system, a mixture with a D2 concentration of 1% can be enriched to 20%, and the D2 recovery rate reaches 90%. Attached Figure Description

[0037] Figure 1 The water vapor adsorption isotherm for carbon materials with different surface chemical properties at a relative humidity ≤10%.

[0038] Figure 2 The mass transfer time of a single column for carbon adsorbents with different surface chemical properties at the same packing height is defined as the time from the breakthrough point to the saturation point.

[0039] Figure 3 The pore size distribution curve of Example 3 was obtained from the 77 KN2 adsorption isotherm.

[0040] Figure 4 The pore size distribution curve of Example 3 is obtained from the CO2 adsorption isotherm at 273 K.

[0041] Figure 5 This is the single-column penetration curve of Example 3.

[0042] Figure 6 The D2 / H2 concentration in the recovered gas was obtained by intermittent mass spectrometry sampling in Example 3.

[0043] Figure 7 This is a schematic diagram simulating a moving bed device.

[0044] Figure 8 This is a schematic diagram illustrating the function of the adsorption column.

[0045] Among them, 1 is the integrated control system, 2 is the control software, 3 is the network cable, 4 is the PLC controller, 5 is the adsorption column, 6 is the solenoid valve, 7 isotope gas control system, 8 is the product collection system, 9 is the gas storage tank, 10 is the mass spectrometer, 11 is the compressor, 12 is the mixed gas pipeline, 13 is the cryogenic control system, 14 is the liquid level controller, 15 is the coolant, 16 is the cold trap, 17 is the vacuum pump, 18 is the mechanical transmission device, 19 is the regeneration zone, 20 is the displacement zone, and 21 is the adsorption zone. Detailed Implementation

[0046] The following embodiments are provided to better understand the present invention and are not intended to limit the scope of the preferred embodiments, nor do they constitute a limitation on the content and protection scope of the present invention. The technical solutions of the present invention will be further described below with reference to specific embodiments.

[0047] Experimental steps or conditions not specified in the examples can be performed by following the procedures or conditions outlined in relevant literature or standard experimental procedures in this field. All reagents and instruments, unless otherwise specified, are commercially available products.

[0048] Examples 1-12: Carbon adsorbents were synthesized according to the following steps. Monomers were weighed according to the specified molar ratio and dissolved in 75 mL of organic solvent to prepare solution A; linker units were weighed according to the specified molar ratio and dissolved in 75 mL of organic solvent to prepare solution B. Solution B was poured into solution A at room temperature and with stirring (400 rpm / min) to form a milky white organic emulsion containing prepolymer.

[0049] Under stirring, triethylamine (the ratio of triethylamine to monomer is 2.9) was added to a milky white organic emulsion containing the prepolymer at a dropping rate of 5 mL / sec. Rapid polymerization was carried out in a thermal environment heated to 60 °C at a speed of 400 rpm / min for 6 hours to obtain a white, light yellow or light green porous carbon precursor polymer.

[0050] The porous carbon precursor polymer was purged under an inert atmosphere at room temperature for 30 min with an inert gas flow rate of 50 mL / min, and then heated to the target temperature at a heating rate of 5 °C and held for 2 hours to obtain a carbon adsorbent with tunable surface chemistry. The preparation conditions, nitrogen content, and pore structure of the carbon adsorbents with tunable surface chemistry in each example are shown in Table 1.

[0051] Table 1 shows the preparation conditions, nitrogen content, and pore structure of the surface chemistry-tunable carbon adsorbents prepared in each example. Example 1 Cyanide Piperazine 2 : 1 800 / 5 19.0 4.1 424 0.52 0.15 0.37 Example 2 Cyanide Piperazine 2 : 3 600 / 5 26.0 4.1 385 0.48 0.13 0.35 Example 3 Cyanide Piperazine 2 : 3 700 / 5 19.7 4.1 560 0.58 0.21 0.37 Example 4 Cyanide Piperazine 2 : 3 800 / 5 14.5 4.1 542 0.55 0.19 0.36 Example 5 Cyanide Piperazine 2 : 3 800 / 3 14.0 4.1 532 0.53 0.16 0.37 Example 6 Cyanide Piperazine 2 : 5 800 / 5 15.1 4.1 512 0.53 0.15 0.38 Example 7 melamine dichloro-p-xylene 2 : 3 800 / 5 8.8 4.1 438 0.48 0.10 0.38 Example 8 p-phenylenediamine terephthaloyl chloride 1 : 1 700 / 5 2.3 4.1 368 0.31 0.09 0.22 Example 9 m-phenylenediamine isophthaloyl chloride 1 : 1 700 / 5 2.1 4.1 323 0.36 0.11 0.21 Example 10 ethylenediamine terephthalaldehyde 1: 1 700 / 5 3.1 4.1 239 0.35 0.07 0.18 Example 11 ethylenediamine glutaraldehyde 1: 1 700 / 5 2.5 4.1 388 0.47 0.12 0.35 Example 12 hydrazine terephthalaldehyde 1: 1 700 / 5 2.8 4.1 276 0.39 0.08 0.31 Example 13 Single-column breakthrough test procedure for surface-chemically tunable carbon adsorbent The surface chemistry-tunable carbon adsorbent was activated at 300 °C for 16 hours under a vacuum of 0.05 torr. The activated carbon adsorbent with adjustable surface chemistry was packed into an adsorption column with a length of 120 mm, a diameter of 8 mm, and an inner diameter of 6 mm, and purged with Ne or He for 1-3 hours.

[0052] A D2 / H2 column penetration curve for a single column was obtained by introducing a gas mixture with a D2 / H2 / Ne ratio of 1:1:8 into a fixed bed.

[0053] As shown in Table 1, Examples 1-12 all have a multi-level porous structure and a high specific surface area. Figure 1-6 It is known that the carbon adsorbent obtained by using cyanuric chloride as a monomer and piperazine as a connecting unit has high nitrogen content, high polarity and hierarchical pore structure, which provides a high selectivity and a fast mass transfer pathway for the D2 / H2 separation process.

[0054] Example 14: SMB Performance Testing of Surface Chemically Tunable Carbon Adsorbents ①Light Isotope Simulation Moving Bed like Figure 7 As shown, the light isotope simulation moving bed includes an isotope gas control system 7, a solenoid valve 6, a cryogenic control system 13, an integrated control system 1, an adsorption column 5, a product collection system 8, and a product detection system. The isotope gas control system 7 includes isotope gas, flow controller and gas mixing pipeline 12. The isotope gas is connected to the flow controller and then to the gas mixing pipeline 12. The gas mixing pipeline 12 is connected to the adsorption column 5. The solenoid valve 6 includes several solenoid valves placed at the top, bottom and sides of the adsorption column 5. The cryogenic control system 13 includes a cold trap 16, a liquid level controller 14, and a mechanical transmission device 18; a coolant 15 is added to the cold trap 16 to keep the temperature of the adsorption column 5 and the corresponding pipeline constant at 77 K-160 K; the mechanical transmission device 18 is a scissor lift to immerse or remove the adsorption column 5 and the corresponding gas pipeline from the cold trap 16. The integrated control system 1 includes control software 2 running on a computer and a PLC controller 4. The computer is connected to the PLC controller 4 via a network cable 3, and the PLC controller is connected to a flow controller and a solenoid valve 6 via a network cable 3 to control the flow rate of the isotope gas, the flow of gas into the adsorption column in the gas mixing pipeline, the flow of product gas out of the adsorption column, and the series or parallel connection mode between the adsorption columns. The specific control logic of the integrated control system 1 is as follows: the target flow rate of the isotope gas is preset in the control software 2, and the PLC controller 4 sends an instruction to the flow controller to set the target flow rate; the control software 2 issues instructions to the PLC controller 4 according to the process requirements, including instructions for gas flowing into the adsorption column, product gas flowing out of the adsorption column, and "series / parallel" switching; the PLC controller 4 triggers the on / off state of the corresponding solenoid valve 6 to realize the on / off of the pipeline for gas flowing into the adsorption column and product gas flowing out of the adsorption column, as well as the switching of the series / parallel connection mode between the adsorption columns. The adsorption column 5 includes at least two adsorption columns for adsorption, two adsorption columns for displacement, and two adsorption columns for regeneration; the adsorption columns for adsorption and the adsorption columns for displacement are connected in series; the gas in the gas mixing pipeline 12 includes a light isotope feed gas and a displacement gas, the light isotope feed gas is connected to the adsorption columns for adsorption, and the displacement gas is connected to the adsorption columns for displacement; the light isotope feed gas includes hydrogen isotopes, oxygen isotopes, methane isotopes, nitrogen isotopes, ammonia isotopes, carbon dioxide isotopes, or rare gas isotopes, and the displacement gas includes heavy component isotopes during the same operation; the hydrogen isotopes include H2 / D2, D2 / T2, H2 / T2, or H2 / D2 / T2; the oxygen isotopes include 16 O2 / 18 O2, the methane isotopes include 12 CH4 / 13 CH4 or 12 CH4 / 12 CD 4； Nitrogen isotopes include 14 N2 / 15 N2; ammonia isotopes include 14 NH3 / 15 NH3 or 14 NH3 / 14 ND3; the carbon dioxide isotopes include 12 CO2 / 13 CO2 or 12 C 16 O2 / 12 C 18 O2; the rare gas isotopes include 3 He / 4 He 20 Ne / 21 Ne / 22Ne or 36 Ar / 38 Ar / 40 Ar.

[0055] The adsorption column is a packed fixed bed made of stainless steel. The dimensions of the adsorption column can be customized according to the processing capacity requirements, with a length of 100 mm and a diameter of 10 mm.

[0056] The adsorption columns that perform regeneration are connected in parallel to increase regeneration efficiency.

[0057] The bottom of the adsorption column used for regeneration is connected to the vacuum pump 17.

[0058] The adsorption columns that perform adsorption are connected in series; the adsorption columns that perform displacement are connected in series.

[0059] The collection system 8 includes a gas storage tank 9, which is connected to the bottom of the adsorption column tower for regeneration via a vacuum pump 17 and a compressor 11.

[0060] The product detection system includes a mass spectrometer 10, which is connected to the bottom of the adsorption column that performs regeneration via a vacuum pump 17. The pressure in the adsorption column is controlled by a vacuum pump and an isotope gas control system, with a pressure adjustment range of 0.001-4 bar.

[0061] ② H2 / D2 separation was performed using an isotope-simulated moving bed. Step 1: Ten adsorption columns were filled with a surface chemically adjustable carbon adsorbent (Examples 1-12) that had been vacuum-activated at 300°C for 16 h under a vacuum of 0.05 torr. Neon gas was used to purge the pipeline and adsorbent to remove impurity gases. The adsorption column 5 was made of stainless steel, with a single column length of 100 mm and a diameter of 10 mm. The carbon adsorbent particle size was 0.1 mm, the filling height was 980 mm, and the filling mass was 23.5 g.

[0062] Step 2: Add liquid nitrogen to the cold trap 16, and use the mechanical transmission device 18 to immerse the adsorption column 5 and the corresponding gas pipeline into the cold trap 16. Wait until the temperature is constant at 77 K, and close the outlet valve of the adsorption column during this process. Continuously introduce neon gas into the adsorption column to maintain the pressure inside the tower at a positive pressure to prevent impurity gases from entering.

[0063] Step 3: The operating program runs on the integrated control system 1. The isotope gas control system 7 introduces a mixed H2 / D2 / Ne gas (10% / 10% / 80%, volume ratio) into the adsorption column performing adsorption, with a Ne flow rate of 110 mL / min. A replacement gas D2 / Ne mixed gas (10% / 90%, volume ratio) is introduced into the adsorption column performing displacement, with a Ne flow rate of 120 mL / min. The liquid level controller 14 automatically replenishes liquid nitrogen to maintain the liquid level. Figure 8 As shown, the operation of adsorption column 5, from left to right, consists of regeneration zone 19, displacement zone 20, and adsorption zone 21. Regeneration zone 19 includes three adsorption columns for regeneration (①-③), displacement zone 20 includes three adsorption columns for displacement (④-⑥), and adsorption zone 21 includes four adsorption columns for adsorption (⑦-⑩). The adsorption columns for regeneration are connected in parallel to improve regeneration efficiency. The adsorption columns for displacement are connected in series, with multi-stage displacement to further enrich heavy components, and are connected in series with the adsorption columns for adsorption to adsorb the discharged D2. The four adsorption columns for adsorption are connected in series, efficiently adsorbing heavy components and discharging light components from the top of the column. The pressure inside the adsorption columns performing adsorption and displacement operations is controlled at 1 bar. Regeneration is performed by vacuum purging, with regeneration consisting of vacuum (10 kPa) and carrier gas purging (40 mL / min Ne).

[0064] Step 4: Every 8 minutes, switch the valves to simulate the movement of the adsorbent. Adsorption column ①, which is undergoing regeneration, performs the adsorption operation originally performed by adsorption column ⑩; adsorption column ⑦, which is undergoing adsorption, performs the displacement operation originally performed by adsorption column ⑥; adsorption column ④, which is undergoing displacement, performs the regeneration operation originally performed by adsorption column ③; and the remaining adsorption columns simulate movement in the same direction. Specifically, adsorption columns ② and ③ perform the regeneration operations originally performed by adsorption columns ① and ②, respectively; adsorption columns ⑤ and ⑥ perform the displacement operations originally performed by adsorption columns ④ and ⑤, respectively; and adsorption columns ⑧, ⑨, and ⑩ perform the adsorption operations originally performed by adsorption columns ⑦, ⑧, and ⑨, respectively.

[0065] Step 5: After 10 cycles, the product detection system detects the composition of the gas flowing out from the tail end of the vacuum pump 17 and collects the product from the gas storage tank 9.

[0066] Following the above method, the purity of D2 in the recovered gas obtained by running the program after loading hydrogen isotopes into a moving bed separation system with adsorbents of different surface chemical properties was compared. The specific performance is shown in Table 2.

[0067] Table 2 shows the hydrogen isotope separation performance of carbon adsorbents with different surface chemical properties.

[0068] Step 6: After running for 800 minutes, shut down the operating program on the integrated control system 1, and use the mechanical transmission device 18 to remove the adsorption column 5 and the corresponding gas pipeline from the cold trap 16, and recover the remaining liquid nitrogen in the cold trap 16 for the next operation.

[0069] The porous carbon with tunable surface chemistry synthesized in Example 8 had a mass transfer time of 78 min and required 40 min to complete regeneration and desorption; Example 2 was completely regenerated and desorbed within 30 min, while Example 3 only required 15 min to complete regeneration and desorption.

[0070] Furthermore, using porous carbon with tunable surface chemistry as described in Example 3, a D2 / H2 mixture with a concentration of 1% D2 (H2 as the balance gas) was used as the light isotope gas source, and Ne was used as the carrier gas (the volume flow rates of the D2 / H2 mixture and Ne were 2 mL / min and 8 mL / min, respectively). After 10 rounds of the above operation, the D2 / H2 mixture with a purity of 1% D2 could be concentrated to 20%, and the D2 recovery rate reached 90%.

[0071] ③ CH4 / CD4 separation was performed using a light isotope-simulated moving bed. Replace the gas component introduced into the adsorption column in step 3 of section ② with... 12 CH4 / 12 A CD4 / Ne mixture (10% / 10% / 90%, volume ratio) was introduced, with a Ne flow rate of 110 mL / min. The replacement gas introduced into the adsorption column for the displacement process was then replaced with... 12 A CD4 / Ne mixture (10% / 90%, volume ratio) was used with a Ne flow rate of 120 mL / min. A level controller 14 automatically added coolant 15 (liquid nitrogen and isopentane) to the cold trap 16, maintaining the mixture temperature at 113 K and ensuring a stable liquid level. Using the 4.1 Å pore size surface chemistry tunable carbon adsorbent synthesized in Example 3, CH4 and CD4 were separated in the gas phase (steps as in ②). Experimental results showed that, under equal volume feed conditions, the purity of CD4 reached 80%, and under vacuum (10 kPa) carrier gas purging (40 mL / min Ne), complete regeneration was achieved within 15 min.

Claims

1. The application of a surface-controlled carbon adsorbent in the separation of light isotopes in a simulated moving bed, characterized in that: The simulated moving bed is used, including the following steps: S1 The adsorption column is filled with pre-activated carbon adsorbent, and the pipeline and adsorbent are purged with inert gas to remove impurity gases. S2 Immerse the adsorption column and corresponding gas pipeline in a coolant at a constant temperature of 77-160 K until the temperature is constant; during this process, close the outlet valve of the adsorption column and continuously introduce inert gas into the adsorption column to maintain the pressure inside the column at a positive pressure to prevent impurity gases from entering. S3. Light isotope feed gas is introduced into at least two adsorption columns performing adsorption, displacement gas is introduced into at least two adsorption columns performing displacement, and at least two adsorption columns performing regeneration are regenerated. S4 operates for 1-15 minutes each time, switching valves to perform different operations on the adsorption columns to simulate the adsorbent moving in the opposite direction to the gas. After the valve is switched, the first adsorption column that was performing adsorption performs a displacement operation, the first adsorption column that was performing displacement performs a regeneration operation, the first adsorption column that was performing regeneration performs an adsorption operation, and the remaining adsorption columns simulate moving in the same direction. Specifically, the Xth adsorption column performs the operation originally performed by the X-1th adsorption column, and when X ≥ 2, the first adsorption column performs the operation originally performed by the last adsorption column. The carbon adsorbent has a hierarchical porous structure with tunable surface chemistry. The nitrogen content is 2-26 at.%, and the surface polarity is such that the water vapor adsorption capacity is 0.1-4.4 mmol / g at a relative humidity of 10%. The micropore size of the carbon adsorbent is distributed around 4.1 Å. The light isotope feed gas includes hydrogen isotopes, oxygen isotopes, methane isotopes, nitrogen isotopes, ammonia isotopes, carbon dioxide isotopes, or rare gas isotopes, and the replacement gas in the same operation includes heavy component isotopes.

2. The application of a surface-controlled carbon adsorbent as described in claim 1 in the separation of light isotopes in a simulated moving bed, characterized in that: The carbon adsorbent has a nitrogen content of 12-26 at.% and exhibits surface polarity, with a water vapor adsorption capacity of 2.2-4.4 mmol / g at a relative humidity of 10%.

3. The application of a surface-controlled carbon adsorbent as described in claim 1 in the separation of light isotopes in a simulated moving bed, characterized in that: The adsorption column for performing adsorption is connected in series with the adsorption column for performing displacement; at least two adsorption columns for performing displacement perform multi-stage displacement to further enrich the heavy components; the light component and heavy component mixed gas flowing out from the top of the adsorption column for performing displacement enter the adsorption column for performing adsorption to further recover the heavy components.

4. The application of a surface-controlled carbon adsorbent as described in claim 1 in the separation of light isotopes in a simulated moving bed, characterized in that: The adsorption columns that perform regeneration are connected in parallel; the adsorption columns that perform adsorption are connected in series; and the adsorption columns that perform displacement are connected in series.

5. The application of a surface-controlled carbon adsorbent as described in claim 1 in the separation of light isotopes in a simulated moving bed, characterized in that: The regeneration includes one or more of purging, vacuum, and vacuum purging.

6. The application of a surface-controlled carbon adsorbent as described in claim 1 in the separation of light isotopes in a simulated moving bed, characterized in that: Step S4 also includes collecting and / or detecting the product after running 5-10 rounds.

7. The application of a surface-controlled carbon adsorbent as described in claim 1 in the separation of light isotopes in a simulated moving bed, characterized in that: The carbon adsorbent is obtained by pyrolyzing a porous carbon precursor polymer formed by a substitution reaction of monomers and linking units; the monomers include one or more of cyanuric chloride, melamine, p-phenylenediamine, hydrazine and its dihydrazine compounds, m-phenylenediamine and ethylenediamine; the linking units include one or more of piperazine, dichloro-p-xylene, terephthaloyl chloride, isophthaloyl chloride, terephthalaldehyde and glutaraldehyde.

8. The application of a surface-controlled carbon adsorbent as described in claim 7 in the separation of light isotopes in a simulated moving bed, characterized in that: The method for preparing the porous carbon precursor polymer specifically includes the following steps: S01 Dissolve the monomer and the linking unit in 50-250 mL of organic solvent to obtain a homogeneous organic solution. At 20-30℃ and a stirring rate of 300-700 rpm / min, slowly pour the organic solution containing the linking unit into the organic solution containing the monomer to obtain a milky white organic emulsion containing the prepolymer. SO2 acid-binding agent is added dropwise to a milky white organic emulsion containing prepolymer at a rate of 1-10 mL / sec; the mixture is heated to 40-80 °C at a speed of 300-700 rpm / min and held for 3-12 h to obtain a porous carbon precursor polymer.

9. The application of a surface-controlled carbon adsorbent as described in claim 1 in the separation of light isotopes in a simulated moving bed, characterized in that: The simulated moving bed includes an isotope gas control system (7), a solenoid valve (6), a cryogenic control system (13), an integrated control system (1), and an adsorption column (5). The isotope gas control system (7) includes an isotope gas, a flow controller and a gas mixing pipeline (12). The isotope gas is connected to the flow controller and then to the gas mixing pipeline (12). The gas mixing pipeline (12) is connected to the adsorption column (5). The solenoid valve (6) includes several solenoid valves placed at the top, bottom and sides of the adsorption column tower; The cryogenic control system (13) includes a cold trap (16), a liquid level controller (14), and a mechanical transmission device (18); a coolant (15) is added to the cold trap (16) to keep the temperature of the adsorption column (5) and the corresponding pipeline constant at 77 K-160 K; the mechanical transmission device (18) is a scissor lift to immerse or remove the adsorption column (5) and the corresponding gas pipeline from the cold trap (16). The integrated control system (1) includes control software (2) running on a computer and a PLC controller (4). The computer is connected to the PLC controller (4) via a network cable (3). The PLC controller (4) is connected to a flow controller and a solenoid valve (6) via a network cable (3) to control the flow rate of isotopic gas, the gas flowing into the adsorption column in the gas mixing pipeline, the product gas flowing out of the adsorption column, and the series or parallel connection mode between adsorption columns.

10. The application of a surface-controlled carbon adsorbent as described in claim 9 in the separation of light isotopes in a simulated moving bed, characterized in that: The gas in the gas mixing pipeline (12) includes light isotope feed gas and displacement gas. The light isotope feed gas is connected to the adsorption column for adsorption, and the displacement gas is connected to the adsorption column for displacement. The pipeline also includes a product collection system (8) and / or a product detection system. The product collection system (8) includes a gas storage tank (9). The gas storage tank (9) is connected to the top of the adsorption column (5) or to the bottom of the adsorption column (5) via a vacuum pump (17). The product detection system includes a mass spectrometer (10). The mass spectrometer (10) is connected to the top of the adsorption column (5) or to the bottom of the column via a vacuum pump (17).

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