A porous adsorbent material for removing neon from helium and its preparation method

Abstract

The present invention relates to the technical field of special gas purification, and specifically discloses a porous adsorption material for removing neon from helium and a preparation method thereof. The method comprises the following steps: (1) preparing a lignin raw material treated by fermentation; (2) preparing a carbon precursor; (3) placing the carbon precursor in a mixed solution containing a metal salt and a surfactant, stirring and impregnating to obtain a carbon precursor impregnated with the metal salt; (4) washing the carbon precursor impregnated with the metal salt to remove the excessively deposited metal salt, and drying to obtain a washed carbon precursor; (5) activating and creating pores in the washed carbon precursor with carbon dioxide at a high temperature to obtain a porous adsorption material for removing neon from helium. The porous carbon adsorption material prepared by the present invention using renewable natural biomass raw materials has a uniformly distributed pore structure and has a high adsorption and capture ability for neon under low-temperature conditions, and can effectively remove neon impurities in helium.

Description

Technical Field

[0001] The present invention belongs to the technical field of special gas purification, and particularly relates to a porous adsorbent for removing neon from helium, a preparation method thereof, and an application thereof. Background Art

[0002] Helium (He) is a colorless and odorless inert gas, which has wide applications in many fields such as semiconductors, medical treatment, military industry, aerospace, etc., and is one of the rare strategic materials indispensable for the development of high-tech industries. With the rapid development of domestic high-tech industries, the market demand for high-purity helium is also increasing day by day.

[0003] Since the content of helium in the air is extremely low, only about 5 ppm, it is difficult to effectively produce helium using traditional air fractionation equipment. Therefore, at present, helium is mainly obtained by gradually condensing natural gas to about -190 °C to obtain crude helium with a purity of 70% - 90%, and then further purifying the crude helium to 99.999% high-purity helium by cryogenic distillation. However, since the boiling point of helium is very low (-268.9 °C), and the boiling point of neon, the main impurity in crude helium, is also relatively low (-248.6 °C), a method of deep cooling is required to separate neon and helium to produce high-purity helium. This is a production process with large equipment investment and extremely high energy consumption. The cryogenic adsorption method can adsorb and remove impurities such as neon in helium in a low-temperature environment, increase the purity of helium to 99.999%, significantly improve the production efficiency of neon, and at the same time greatly reduce the production energy consumption.

[0004] Chinese invention patent application CN202311869986.1 discloses a cryogenic pressure swing adsorption method for efficiently removing neon and hydrogen from helium. The raw gas containing helium and impurity gases can reduce the concentrations of neon and hydrogen to below 4 ppm and 1 ppm respectively through the designed pressure swing adsorption process. However, at present, the commercial activated carbon adsorbent has a low adsorption capacity for neon, resulting in difficult improvement of production efficiency.

[0005] Porous carbon materials have the advantages of large specific surface area and pore volume, stable structure and low production cost, and have broad application prospects in the field of gas separation and purification. Activated carbon is one of the most commonly used raw materials for existing low-temperature adsorbents. The temperature is 60-77K near the liquid nitrogen temperature zone, and it has been industrialized. However, powdered activated carbon usually has a very high specific surface area and rich microporous structure, which makes them excellent in gas adsorption; but in order to make powdered activated carbon into easy-to-handle block or granular materials, it is usually necessary to add a binder, which may fill or cover the micropores of the activated carbon, thereby reducing the effective adsorption sites, reducing the adsorption capacity and selectivity. At present, the porous carbon materials used to produce high-purity helium are mostly commercial activated carbons with a wide pore size distribution, which leads to their low adsorption capacity for the inert gas neon, greatly limiting the efficiency of producing high-purity helium by low-temperature adsorption. The carbon-based adsorbents directly prepared by the current methods on the market often lack sufficient mechanical strength and are easily broken into powder during operation, resulting in decreased adsorption performance; the direct preparation method may lead to uneven pore size distribution, affecting the selectivity and adsorption efficiency of specific gases. Therefore, the current low-temperature adsorption method still has small adsorption capacity and low recovery rate. At the same time, the effect of current adsorbents under low pressure cannot meet the needs of consumers.

[0006] Therefore, there is an urgent need for a porous carbon material with uniform pore size distribution and high adsorption capacity for the inert gas neon at low temperature and a preparation method thereof. Summary of the invention

[0007] Based on the deficiencies of the prior art, the present invention provides a porous carbon material with uniform pore size distribution and high adsorption capacity for inert gas neon at low temperature and a preparation method thereof.

[0008] In order to achieve the above object, the present invention provides the following technical solutions:

[0009] A method for preparing a porous adsorption material for removing neon from helium comprises the following steps:

[0010] (1) crushing the lignin raw material to less than 200 meshes to obtain powder; mixing 20-30 parts of the powder and 40-50 parts of deionized water by weight to obtain a fermentation material, inoculating the fermentation material with mixed microorganisms for aerobic fermentation, filtering, drying, crushing, screening, and obtaining a fermented lignin raw material; the mixed microorganisms include Bacillus licheniformis, Bacillus subtilis, and Rhizopus oryzae;

[0011] (2) Mix 1 part by weight of the fermented lignin raw material with 10 - 12 parts by weight of 1 - 1.2 mol / L hydrochloric acid, ultrasonically disperse it at a power of 90 - 100 W for 40 - 50 min, then stir at a speed of 600 - 650 rpm at 80 - 85 °C for 25 - 30 h, wash with deionized water until neutral, and vacuum dry at 80 - 90 °C in a vacuum drying oven for 24 - 28 h to obtain a carbon precursor;

[0012] (3) Place the carbon precursor in a mixed solution containing metal salts and surfactants and stir to impregnate to obtain a carbon precursor impregnated with metal salts;

[0013] (4) Wash the carbon precursor impregnated with metal salts to remove the excessively deposited metal salts and dry to obtain a washed carbon precursor;

[0014] (5) Activate and pore the washed carbon precursor with carbon dioxide to obtain a porous adsorbent material for removing neon from helium, labeled as MC.

[0015] Further, the dosage of Bacillus licheniformis in step (1) is 10 8 - 10 9 CFU / mL of fermentation material; the dosage of Bacillus subtilis is 10 6 - 10 7 CFU / mL of fermentation material; the dosage of Rhizopus oryzae is 10 6 - 10 7 CFU / mL of fermentation material.

[0016] The porous adsorbent material prepared by first fermenting the lignin raw material using a composite microorganism in the present invention can improve the neon adsorption capacity of the porous adsorbent material under the condition of 10000 Pa. Bacillus licheniformis, Bacillus subtilis, and Rhizopus oryzae can secrete various enzymes during aerobic fermentation, which can partially degrade the complex structure inside the lignin raw material. After fermentation treatment, its molecular chain is partially broken, chemical bonds are broken, the structure of lignin is changed, providing a more abundant microporous and mesoporous structure. The synergistic effect of these pores can significantly increase the specific surface area of the adsorbent material. A larger specific surface area means more adsorption sites, thereby improving the adsorption capacity of the adsorbent material for neon.

[0017] Further, the lignin raw material in step (1) includes coconut shell, olive shell, and bamboo in a weight ratio of 1: (1.3 - 1.5): (0.5 - 0.7).

[0018] When using coconut shells, olive shells, and bamboo with specific ratios as lignin raw materials, the neon adsorption capacity under 1000 Pa conditions can be further improved. This is mainly because the lignin content and structure in coconut shells, olive shells, and bamboo are different. Coconut shells are prone to forming larger mesopores and macropores during fermentation and activation, which helps the diffusion and adsorption of gas molecules; olive shells are more likely to form micropores, and these micropores can provide more high-energy adsorption sites, which are particularly suitable for adsorbing neon; bamboo can form uniformly distributed micropores and mesopores during fermentation and activation, and this diversity of pore structures helps to increase the specific surface area and adsorption selectivity of the adsorption material. The complementarity of different raw materials, the synergistic effect of microbial metabolites, the optimized pore structure and adsorption sites, as well as the improved mechanical strength and stability, work together to make the adsorption material exhibit higher adsorption performance under medium partial pressure conditions. This improvement not only increases the adsorption capacity of the adsorption material but also enhances its selectivity and stability.

[0019] Bacillus licheniformis, purchased from Shanghai Microbial Preservation Co., Ltd., product number: SHMCCD10742.

[0020] Bacillus subtilis, purchased from Shanghai Microbial Preservation Co., Ltd., product number: SHMCCD15537.

[0021] Rhizopus oryzae, purchased from Shanghai Microbial Preservation Co., Ltd., product number: SHMCCD10257.

[0022] Further, the fermentation conditions in step (1) are: fermenting at 32 - 35 °C for 5 - 8 hours.

[0023] Further, the surfactant in step (3) includes sodium dodecylbenzenesulfonate, octadecyl dimethyl betaine, and zwitterionic surfactant with a weight ratio of 1:(1.2 - 1.4):(0.3 - 0.5); the mass fraction of the surfactant in the mixed solution is 0.5 - 2.5%.

[0024] Further, the preparation method of the zwitterionic surfactant includes the following steps:

[0025] Step 1: Heat the HCl aqueous solution to 40 - 45 °C, dropwise add N,N-dimethylhexadecylamine, keep the temperature for reaction for 1 - 1.5 h, then dropwise add the ethanol solution of epoxidized soybean oil, control the temperature at 50 - 55 °C, react for 6 - 8 h, and remove ethanol and water by vacuum distillation to obtain intermediate 1; calculated by molar ratio, N,N-dimethylhexadecylamine:HCl:epoxidized soybean oil = 3:3:(0.8 - 1);

[0026] Step 2: Take 10 parts by weight of the intermediate 1 and dissolve it in an ethanol aqueous solution. Add 0.5 - 0.7 parts by weight of NaOH, reflux and stir for 4 - 6 h, stop the reaction, filter, wash the filter residue with absolute ethanol 3 - 4 times, and dry it under vacuum to obtain the zwitterionic surfactant.

[0027] In the present invention, by adding a surfactant with a specific ratio to the impregnation solution, the adsorption capacity of neon gas at low pressure (100 Pa) can be improved. The addition of the surfactant used in the present invention can play a dispersing role during the metal salt deposition process, prevent the aggregation of metal salt particles, ensure their uniform distribution on the surface and inside the pores of the carbon precursor prepared in the present invention, and can further optimize the pore structure, increase the adsorption sites, and improve the adsorption selectivity, which helps to maintain the openness of the pores and avoid pore blockage.

[0028] Further, the metal salt described in step (3) is selected from one or more of sodium salts, potassium salts, magnesium salts, and zinc salts.

[0029] Further, the concentration of the metal salt in the mixed solution described in step (3) is 1 - 5 mol / L.

[0030] Further, the conditions for the stirring impregnation in step (3) are: the impregnation time is 20 - 24 h, the temperature is 60 - 80 °C, and the stirring speed is 200 - 300 rpm.

[0031] Further, the impregnation solid-liquid ratio of the carbon precursor and the mixed solution in step (3) is 1 g:15 mL to 1 g:20 mL.

[0032] Further, in step (5), the activation for pore formation is to heat up the washed carbon precursor and use carbon dioxide for activation for pore formation. The heating rate is 5 - 10 °C / min, the activation temperature is 800 - 1000 °C, the activation duration is 80 - 100 min, and the carbon dioxide concentration is 80 - 100%.

[0033] The present invention provides a porous adsorption material for removing neon from helium prepared by the described preparation method.

[0034] Compared with the prior art, the present invention has the following advantages and technical effects:

[0035] (1) In the present invention, bamboo, coconut shell, and olive shell containing lignin are used as carbon sources, and the method of in-situ directional activation for pore formation with metal ions is adopted. During the physical activation for pore formation of the porous carbon material, highly dispersed metal ions are used to in-situ etch and activate the porous carbon material, thereby controlling the activation for pore formation reaction of the porous carbon material, preparing a porous carbon adsorption material with a uniform pore size distribution, having a high adsorption and capture ability for neon gas under low-temperature conditions, and effectively removing neon impurities in helium.

[0036] (2) The porous adsorbent material for removing neon from helium provided by the present invention can use natural biomass materials as carbon sources, which are green, environmentally friendly, renewable, and have low production and manufacturing costs. The adsorbent material of the present invention uses the method of in-situ directional activation of metal ions to form pores, and precisely etches uniform pore diameters on the carbon material. Compared with commercial activated carbon, the pore size distribution of the adsorbent material of the present invention is more uniform, making it have stronger neon adsorption capacity.

[0037] (3) The porous adsorbent material prepared by the present invention through the fermentation treatment of lignin raw materials using composite microorganisms can improve the neon adsorption capacity of the porous adsorbent material under the condition of 10,000 Pa. Compared with existing adsorbent materials, the adsorbent material of the present invention can adsorb 0.87 mmol / g of neon at 0.1 bar at low temperature, which is much higher than 0.45 mmol / g of commercial coconut shell CTC100 activated carbon.

[0038] (4) When using coconut shell, olive shell and bamboo with a specific ratio as lignin raw materials, the neon adsorption capacity under the condition of 1,000 Pa can be further improved.

[0039] (5) By adding a surfactant with a specific ratio to the impregnation solution, the present invention can improve the adsorption capacity of neon at low pressure (100 Pa). The adsorbent material of the present invention can have excellent adsorption effects under low temperature and low pressure conditions. Description of the Drawings

[0040] Figure 1 It is a typical pore size distribution diagram of commercial coconut shell activated carbon CTC100 and the adsorbent material obtained in Example 4.

[0041] Figure 2 It is the C3H8 and CH3F adsorption isotherms of commercial coconut shell activated carbon CTC100 and the adsorbent materials obtained in Examples 1-5 of the present invention at 298K. In the figure, MC-1 is the porous adsorbent material prepared in Example 1, MC-2 is the porous adsorbent material prepared in Example 2, MC-3 is the porous adsorbent material prepared in Example 3, MC-4 is the porous adsorbent material prepared in Example 4, and MC-5 is the porous adsorbent material prepared in Example 5. Detailed Embodiments

[0042] The present invention will be further described in detail below in conjunction with the drawings and examples, but the scope claimed by the present invention is not limited to the scope described in the examples.

[0043] The raw materials used in the present invention are all commercially available products:

[0044] Bacillus licheniformis, purchased from Shanghai Microbial Preservation Co., Ltd., product number: SHMCCD10742.

[0045] Bacillus subtilis was purchased from Shanghai Baocang Microorganism Co., Ltd., product number: SHMCCD15537.

[0046] Rhizopus oryzae was purchased from Shanghai Baocang Microbiology Co., Ltd., product number: SHMCCD10257.

[0047] Epoxidized soybean oil was purchased from Shandong Kexing Chemical Co., Ltd., industrial grade epoxidized soybean oil.

[0048] Aspergillus niger was purchased from Shanghai Baocang Microbiology Co., Ltd., product number: SHMCC D11656.

[0049] Candida utilis was purchased from Wuhan Huizao Biotechnology Co., Ltd., catalog number: HZB119504.

[0050] Example 1

[0051] This embodiment provides a porous adsorption material for removing neon from helium, and the preparation method thereof comprises the following steps:

[0052] (1) crushing the lignin raw material to less than 200 meshes to obtain powder; mixing 20 parts of the powder and 50 parts of deionized water by weight to obtain a fermentation material, inoculating the fermentation material with mixed microorganisms for aerobic fermentation under the following fermentation conditions: fermentation at 32° C. for 8 hours; filtering, drying, crushing and screening powder between 100 and 200 meshes to obtain a fermented lignin raw material; the mixed microorganisms include Bacillus licheniformis, Bacillus subtilis and Rhizopus oryzae;

[0053] The lignin raw materials include coconut shells, olive shells and bamboo in a weight ratio of 1:1.3:0.5.

[0054] The dosage of Bacillus licheniformis is 10 8 CFU / mL fermentation feed; the dosage of Bacillus subtilis is 10 7 CFU / mL fermentation feed; the dosage of Rhizopus oryzae is 10 6 CFU / mL fermentation feed.

[0055] (2) Mixing 1 part by weight of the fermented lignin raw material and 12 parts by weight of 1 mol / L hydrochloric acid, ultrasonically dispersing the mixture at a power of 100 W for 40 min, stirring the mixture at 85 ° C and a speed of 600 rpm for 30 h, washing the mixture with deionized water until neutral, and vacuum drying the mixture in a vacuum drying oven at 80 ° C for 28 h to obtain a carbon precursor;

[0056] (3) Immerse the carbon precursor in a mixed solution containing metal salt and surfactant with stirring. The conditions for stirring immersion are as follows: the immersion time is 20 h, the temperature is 80 °C, and the stirring speed is 200 rpm. The immersion solid-liquid ratio of the carbon precursor to the mixed solution is 1 g:15 mL; the carbon precursor impregnated with metal salt is obtained;

[0057] The metal salt is potassium chloride; the concentration of the metal salt in the mixed solution is 5 mol / L; the surfactant includes sodium dodecylbenzenesulfonate, octadecyl dimethyl betaine and zwitterionic surfactant with a weight ratio of 1:1.2:0.3; the mass fraction of the surfactant in the mixed solution is 1%; the balance of the mixed solution is water.

[0058] The preparation method of the zwitterionic surfactant includes the following steps:

[0059] Step 1: Heat 100 mL of 5.5 mol / L HCl aqueous solution to 40 °C, dropwise add 0.5 mol of N,N-dimethylhexadecylamine, keep the temperature for reaction for 1.5 h, then dropwise add 1.5 mol of ethanol solution containing 55% by volume of epoxidized soybean oil, control the temperature at 55 °C, react for 6 h, and remove ethanol and water by vacuum distillation to obtain intermediate 1;

[0060] Step 2: Take 10 g of the intermediate 1 and dissolve it in 220 mL of 90% by volume ethanol aqueous solution, add 0.7 g of NaOH, reflux and stir for 4 h, stop the reaction, filter, wash the filter residue with anhydrous ethanol three times, and dry it under vacuum to obtain the zwitterionic surfactant.

[0061] (4) Wash the carbon precursor impregnated with metal salt with water to remove the excessive deposited metal salt, and dry it to obtain the washed carbon precursor;

[0062] (5) Activate and pore the washed carbon precursor with carbon dioxide at high temperature. The heating rate of high-temperature activation is 10 °C / min, the activation temperature is 800 °C, the activation duration is 100 min, and the carbon dioxide concentration is 80%; a porous adsorbent material for removing neon from helium is obtained.

[0063] Example 2

[0064] The difference between this example and Example 1 is that in step (3), the surfactant includes sodium dodecylbenzenesulfonate, octadecyl dimethyl betaine and zwitterionic surfactant with a weight ratio of 1:1.2:0.3; the preparation method of the zwitterionic surfactant is the same as that in Example 1.

[0065] Example 3

[0066] The difference between this embodiment and embodiment 1 is that the lignin raw material includes coconut shell, olive shell and bamboo in a weight ratio of 1:1.3:0.5.

[0067] Example 4

[0068] This embodiment provides a porous adsorption material for removing neon from helium, and the preparation method thereof comprises the following steps:

[0069] (1) crushing the lignin raw material to less than 200 meshes to obtain powder; mixing 25 parts of the powder and 45 parts of deionized water by weight to obtain a fermentation material, inoculating mixed microorganisms into the fermentation material for aerobic fermentation under the following fermentation conditions: fermentation at 33° C. for 6 hours; filtering, drying, and crushing to 100-200 meshes to obtain a fermented lignin raw material; the mixed microorganisms include Bacillus licheniformis, Bacillus subtilis, and Rhizopus oryzae;

[0070] The lignin raw materials include coconut shell, olive shell and bamboo in a weight ratio of 1:1.4:0.6.

[0071] The dosage of Bacillus licheniformis is 10 8 CFU / mL fermentation feed; the dosage of Bacillus subtilis is 10 7 CFU / mL fermentation feed; the dosage of Rhizopus oryzae is 10 6 CFU / mL fermentation feed.

[0072] (2) 1 part by weight of the fermented lignin raw material and 11 parts by weight of 1.1 mol / L hydrochloric acid were mixed, ultrasonically dispersed at a power of 95 W for 45 min, stirred at 82 ° C and a speed of 620 rpm for 27 h, washed with deionized water until neutral, and vacuum dried in a vacuum drying oven at 85 ° C for 26 h to obtain a carbon precursor;

[0073] (3) placing the carbon precursor in a mixed solution containing a metal salt and a surfactant and stirring and impregnating the carbon precursor. The stirring and impregnation conditions are: impregnation time is 22 hours, temperature is 70°C, and stirring speed is 250rpm. The impregnation solid-liquid ratio of the carbon precursor and the mixed solution is 1:18g / mL; obtaining a metal salt-impregnated carbon precursor;

[0074] The metal salt is sodium chloride. The concentration of the metal salt in the mixed solution is 2 mol / L.

[0075] The surfactant comprises sodium dodecylbenzene sulfonate, octadecyl dimethyl betaine and a zwitterionic surfactant in a weight ratio of 1:1.3:0.4; the mass fraction of the surfactant in the mixed solution is 2%.

[0076] The preparation method of the zwitterionic surfactant comprises the following steps:

[0077] Step 1: Heat 100 mL of 5.2 mol / L HCl aqueous solution to 42 °C, add 0.5 mol of N,N-dimethylhexadecylamine dropwise, keep the temperature for reaction for 1.2 h, then add 1.5 mol of ethanol solution containing 58% by volume of epoxidized soybean oil dropwise, control the temperature at 52 °C, react for 7 h, and remove ethanol and water by vacuum distillation to obtain Intermediate 1;

[0078] Step 2: Take 10 g of the Intermediate 1 and dissolve it in 210 mL of ethanol aqueous solution with a volume fraction of 92%, add 0.6 g of NaOH, reflux and stir for 5 h, stop the reaction, filter, wash the filter residue 4 times with absolute ethanol, and dry it under vacuum to obtain the zwitterionic surfactant.

[0079] (4) Wash the carbon precursor impregnated with the metal salt with water to remove the excessive deposited metal salt, and dry it to obtain the washed carbon precursor;

[0080] (5) Activate and pore the washed carbon precursor with carbon dioxide at high temperature. The heating rate of the high-temperature activation is 7 °C / min, the activation temperature is 900 °C, the activation duration is 90 min, and the carbon dioxide concentration is 90%; obtain the porous adsorption material for removing neon from helium.

[0081] Example 5

[0082] The difference between this example and Example 1 is that the dosage of Bacillus licheniformis in step (1) is 10 9 CFU / mL of fermentation material; the dosage of Bacillus subtilis is 10 7 CFU / mL of fermentation material; the dosage of Rhizopus oryzae is 10 7 CFU / mL of fermentation material.

[0083] Comparative Example 1

[0084] The difference between this comparative example and Example 4 is that the surfactant in step (3) includes sodium dodecylbenzenesulfonate, octadecyl dimethyl betaine and zwitterionic surfactant with a weight ratio of 1:1:1; the preparation method of the zwitterionic surfactant is the same as that in Example 1.

[0085] Comparative Example 2

[0086] The difference between this comparative example and Example 4 is that the surfactant in step (3) includes sodium lauryl polyoxyethylene ether sulfate (purchased from Jinan Saijia Chemical Co., Ltd.), ammonium monoglyceride sulfate (CAS: 61789-03-5) and sodium dodecyl sulfate with a weight ratio of 1:1.2:0.3.

[0087] Comparative Example 3

[0088] The difference between this comparative example and Example 4 is that the mixed microorganisms include Candida utilis, Bacillus subtilis, and Aspergillus niger; the dosage of Candida utilis is 10 8 CFU / mL of fermentation material; the dosage of Bacillus subtilis is 10 7 CFU / mL of fermentation material; the dosage of Aspergillus niger is 10 6 CFU / mL of fermentation material.

[0089] Comparative Example 4

[0090] The difference between this comparative example and Example 4 is that the conditions for stirring impregnation are: the impregnation time is 15 h, the temperature is 85 °C, and the stirring speed is 400 rpm; the impregnation solid-liquid ratio of the carbon precursor and the mixed solution is 1:10 g / mL.

[0091] Comparative Example 5

[0092] The difference between this comparative example and Example 4 is that in step (5), the heating rate for high-temperature activation is 15 °C / min, the activation temperature is 600 °C, the activation duration is 60 min, and the carbon dioxide concentration is 50%.

[0093] Comparative Example 6

[0094] The difference between this comparative example and Example 4 is that no fermentation treatment is carried out.

[0095] (1) Mix 1 part by weight of lignin raw material and 11 parts by weight of 1.1 mol / L hydrochloric acid, ultrasonically disperse for 45 min at a power of 95 W, then stir at 82 °C at a speed of 620 rpm for 27 h, wash with deionized water until neutral, and vacuum dry at 85 °C in a vacuum drying oven for 26 h to obtain a carbon precursor;

[0096] (2) Place the carbon precursor in a mixed solution containing metal salt and surfactant and stir for impregnation. The conditions for stirring impregnation are: the impregnation time is 22 h, the temperature is 70 °C, and the stirring speed is 250 rpm. The impregnation solid-liquid ratio of the carbon precursor and the mixed solution is 1:18 g / mL; obtain a carbon precursor impregnated with metal salt;

[0097] The metal salt is sodium chloride. The concentration of the metal salt in the mixed solution is 2 mol / L.

[0098] The surfactant includes sodium dodecylbenzenesulfonate, octadecyl dimethyl betaine, and zwitterionic surfactant with a weight ratio of 1:1.3:0.4;

[0099] The preparation method of the zwitterionic surfactant includes the following steps:

[0100] Step 1: Heat 100 mL of 5.2 mol / L HCl aqueous solution to 42 °C, add 0.5 mol of N,N-dimethylhexadecylamine, keep the temperature for reaction for 1.2 h, then add 1.5 mol of ethanol solution containing 58% by volume of epoxidized soybean oil, control the temperature at 52 °C, react for 7 h, and remove ethanol and water by vacuum distillation to obtain Intermediate 1;

[0101] Step 2: Dissolve 10 g of the Intermediate 1 in 210 mL of ethanol aqueous solution with a volume fraction of 92%, add 0.6 g of NaOH, reflux and stir for 5 h, stop the reaction, filter, wash the filter residue with absolute ethanol 4 times, and dry it under vacuum to obtain the zwitterionic surfactant.

[0102] (3) Wash the carbon precursor impregnated with metal salt to remove the excessive deposited metal salt, and dry it to obtain the washed carbon precursor;

[0103] (4) Activate and pore the washed carbon precursor with carbon dioxide at high temperature. The heating rate of high-temperature activation is 7 °C / min, the activation temperature is 900 °C, the activation duration is 90 min, and the carbon dioxide concentration is 90%; obtain the porous adsorption material for removing neon from helium.

[0104] Performance Test

[0105] 1. Analyze the pore size distribution of commercial coconut shell activated carbon CTC100 and the porous carbon adsorption material MC prepared in Example 4 by using the ASAP2460 multi-station full-automatic specific surface and pore size analyzer of Micromeritics Company in the United States. The results are shown in Figure 1 , and the results show that the pore size of the porous carbon adsorption material MC prepared in Example 4 of the present invention is concentrated at 6.8 Å. By using highly dispersed metal ions, the carbon material can be etched directionally to form pores, so that the prepared porous carbon adsorption material MC has a uniform and concentrated pore size distribution and excellent adsorption capacity for neon.

[0106] 2. Use the 3Flex three-station gas adsorption instrument of Micromeritics Company in the United States to measure the neon adsorption amount of commercial coconut shell activated carbon CTC100, the porous carbon adsorption materials prepared in Examples 1-5 and Comparative Examples 1-6 at 77 K under the partial pressures of 10000 Pa, 1000 Pa, and 100 Pa, and the neon adsorption isotherms of Examples 1-5. The results are shown in Table 1 and Figure 2 .

[0107] Table 1. Test results of neon adsorption amount at 77 K (mmol / g)

[0108]

[0109] The results show that the porous carbon adsorption materials prepared in Examples 1-5 have higher neon adsorption amounts than the commercial coconut shell activated carbon CTC100 at different partial pressures. In particular, the overall adsorption effect of Example 4 is the best.

[0110] In the comparative examples, since the necessary technical solutions were not adopted, their corresponding performance tests were significantly worse than those of the examples. In Comparative Example 1, the ratio of the surfactant was changed. In Comparative Example 2, the type of the surfactant was changed. It can be seen that the adsorption capacity effect of neon at low pressure (100 Pa) decreased. In Comparative Example 3, the types of the mixed microorganisms were different. In Comparative Example 6, no fermentation treatment was carried out, and the neon adsorption amount of the porous adsorption material decreased under the condition of 10,000 Pa. In Comparative Example 4, the stirring impregnation conditions were different, and the adsorption amounts at different pressures all decreased, indicating that the stirring impregnation conditions would affect the in-situ directional activation pore-forming effect of metal ions. In Comparative Example 5, the high-temperature activation conditions were different, and the adsorption amounts at different pressures all decreased, indicating that the high-temperature activation conditions would affect the structure of the porous adsorption material, thereby affecting the adsorption effect. The above experimental results further prove the importance of the technical solutions defined in the present invention for its technical effects.

[0111] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a porous adsorption material for removing neon from helium, characterized in that: The following steps are involved: (1) crushing a lignin raw material to obtain a powder; mixing 20-30 parts of the powder with 40-50 parts of deionized water by weight to obtain a fermentation material, inoculating the fermentation material with mixed microorganisms for aerobic fermentation, filtering, drying, crushing, screening, and obtaining a fermented lignin raw material; the mixed microorganisms are Bacillus licheniformis, Bacillus subtilis, and Rhizopus oryzae; the lignin raw material is coconut shell, olive shell, and bamboo in a weight ratio of 1: (1.3-1.5): (0.5-0.7); (2) Mixing 1 part by weight of the fermented lignin raw material and 10-12 parts by weight of hydrochloric acid, ultrasonically dispersing for 40-50 minutes, stirring at 80-85° C. for 25-30 hours, washing with deionized water until neutral, and vacuum drying to obtain a carbon precursor; (3) placing a carbon precursor in a mixed solution containing a metal salt and a surfactant, stirring and impregnating the carbon precursor to obtain a metal salt-impregnated carbon precursor; wherein the metal salt is selected from one or more of sodium salt, potassium salt, magnesium salt and zinc salt; the surfactant is sodium dodecylbenzene sulfonate, octadecyl dimethyl betaine and zwitterionic surfactant in a weight ratio of 1: (1.2-1.4): (0.3-0.5); the stirring and impregnation conditions are: the impregnation time is 20-24h, the temperature is 60-80°C, and the stirring speed is 200-300rpm; the impregnation solid-liquid ratio of the carbon precursor and the mixed solution is 1:15-1:20g / mL; The preparation method of the zwitterionic surfactant comprises the following steps: step 1, heating an aqueous solution of HCl to 40-45°C, adding N,N-dimethylhexadecylamine dropwise, keeping the temperature for reaction for 1-1.5h, then adding an ethanol solution of epoxy soybean oil dropwise, controlling the temperature at 50-55°C, reacting for 6-8h, and removing ethanol and water by reduced pressure distillation to obtain an intermediate 1; in terms of molar ratio, N,N-dimethylhexadecylamine:HCl:epoxidized soybean oil=3:3:(0.8-1); step 2, taking 10 parts by weight of the intermediate 1 and dissolving it in an ethanol aqueous solution, adding 0.5-0.7 parts by weight of NaOH, reflux stirring for 4-6h, stopping the reaction, filtering, washing the filter residue with anhydrous ethanol, and vacuum drying to obtain a zwitterionic surfactant; (4) washing the carbon precursor impregnated with the metal salt to remove the excess deposited metal salt, and drying to obtain a cleaned carbon precursor; (5) The cleaned carbon precursor is activated with carbon dioxide to form pores, so as to obtain a porous adsorption material from which neon gas in helium gas has been removed; the activation and pore formation is performed by heating the cleaned carbon precursor and activating it with carbon dioxide to form pores, the heating rate is 5-10°C / min, the activation temperature is 800-1000°C, the activation time is 80-100min, and the carbon dioxide concentration is 80-100%.

2. The method for preparing a porous adsorbent material for removing neon from helium according to claim 1, characterized in that: The amount of Bacillus licheniformis used in step (1) is 10 8 -10 9 CFU / mL fermentation feed; the dosage of Bacillus subtilis is 10 6 -10 7 CFU / mL fermentation feed; the dosage of Rhizopus oryzae is 10 6 -10 7 CFU / mL fermentation feed.

3. The method for preparing a porous adsorbent material for removing neon from helium according to claim 1, characterized in that: The fermentation conditions in step (1) are: fermentation at 32-35° C. for 5-8 hours.

4. The method for preparing a porous adsorbent material for removing neon from helium according to claim 1, characterized in that: The concentration of the metal salt in the mixed solution is 1-5 mol / L.

5. A porous adsorption material for removing neon from helium obtained by the preparation method according to any one of claims 1 to 4.

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