A green preparation method for carbon molecular sieve for screening and separating nitrogen and hydrogen

Abstract

The present invention belongs to the field of gas adsorption and separation technology, and discloses a green preparation method of a carbon molecular sieve for screening and separating nitrogen and hydrogen. The preparation method includes: treating a biomass carbon source with a metal salt compound, then pyrolyzing in a tubular furnace, and finally using 2,4,6-tris (2-imidopyrimidine-5-formic acid)-1,3,5-s-triazine surface modification to obtain a carbon molecular sieve for screening and separating nitrogen and hydrogen. Introducing nano-metal particles such as zinc, iron, and copper into the carbon molecular sieve can be used as hydrogen absorption sites, while introducing a large number of active groups such as carboxyl and triazine on the surface of the carbon molecular sieve, which has a strong interface interaction with hydrogen, and further improves the adsorption capacity of the carbon molecular sieve for hydrogen. The obtained carbon molecular sieve has almost no adsorption capacity for nitrogen, and the adsorption rate for hydrogen reaches 6.27-7.06mmol / g; it shows a good effect of adsorbing hydrogen and screening and separating nitrogen and hydrogen.

Description

Technical Field

[0001] The invention belongs to the technical field of gas adsorption and separation, and in particular to a green preparation method of a carbon molecular sieve for screening and separating nitrogen and hydrogen. Background Art

[0002] As an important component of electronic bulk gases, high-purity nitrogen is increasingly used in the electronics, polysilicon and other industries. Hydrogen, as an important green energy source, has a sharp increase in demand. At present, high-purity nitrogen is mainly obtained from nitrogen production equipment through cryogenic distillation. However, the gas obtained in this process is often mixed with permanent gases such as hydrogen. These gases are difficult to remove impurities, and the removal is energy-intensive and difficult. With the increasing requirements for the purity of high-purity gases, the control of impurity content in the gas and the energy consumption of the purification process has become more stringent. Therefore, more efficient nitrogen purification and hydrogen extraction technologies are particularly important.

[0003] In the process of nitrogen purification and impurity removal, the purification process is quite challenging due to the similarity of the physicochemical properties between hydrogen and nitrogen. The traditional removal method mainly uses catalytic conversion technology. However, the catalytic conversion method may introduce new impurities such as water and oxygen, which requires secondary treatment and puts higher requirements on the design of the purification process. At the same time, as an important resource in the field of contemporary new energy, hydrogen has attracted much attention for its high energy density, renewability and pollution-free characteristics. Recovering hydrogen from large-scale nitrogen industrial production facilities can not only obtain ultra-pure nitrogen products, but also provide high-quality hydrogen for hydrogen energy terminals, which has far-reaching significance for promoting the development of the hydrogen energy field. At present, the mainstream technologies for the separation of hydrogen and nitrogen include membrane separation, cryogenic separation and adsorption separation. However, membrane separation technology is limited by short service life and low hydrogen permeation flux in industrial applications; cryogenic separation requires a lot of energy consumption, which is contrary to the original intention of hydrogen energy utilization; and the key to pressure swing adsorption technology lies in the selectivity of the adsorbent. Screening separation technology has attracted much attention for its excellent selectivity. Therefore, the research and preparation of efficient adsorbents that can screen hydrogen and nitrogen has broad industrial application prospects in the fields of nitrogen purification and hydrogen enrichment and impurity removal.

[0004] Asphalt-based porous carbon adsorbents have good technical maturity. Asphalt is a by-product of the petrochemical industry and is also a mineral carbon source with a wide range of sources, low price, and rich surface functional groups. Among them, the commonly used petroleum asphalt is mainly composed of three components: asphaltene, oil, and resin. Asphalt is fluid when the temperature rises, and it loses weight rapidly due to the volatilization of oil. This brings high pollution, high energy consumption, long preparation time, and complex operation to the preparation of asphalt-based porous carbon adsorbents. The resulting product has a low residual carbon content and is difficult to form a highly selective screening channel structure. In contrast, biomass carbon sources have the advantages of being green, environmentally friendly, and renewable. Biomass activated carbon adsorbents such as coconut shell charcoal are also widely used in environmental pollution control due to their simple preparation methods and high adsorption capacity. However, the adsorption selectivity technical indicators of such materials face challenges, and there are few reports on their use in chemical separation and screening separation of hydrogen and nitrogen. Therefore, in the technical field of hydrogen extraction and high-purity nitrogen preparation, it is urgent to develop new carbon molecular sieves with screening separation performance to meet the growing demand for industrial applications. Summary of the invention

[0005] The invention solves the problem that the traditional carbon molecular sieve has poor screening and separation effect on nitrogen and hydrogen and poor selective adsorption effect on hydrogen.

[0006] The technical solution of the present invention is: a green preparation method of a carbon molecular sieve for screening and separating nitrogen and hydrogen, comprising the following steps:

[0007] (1) The biomass carbon source is treated with a metal salt compound to obtain a metal-treated biomass carbon source.

[0008] (2) Placing the metal-treated biomass carbon source in a tubular furnace, pyrolyzing it in a specific gas atmosphere, and then activating it in an inert gas atmosphere to obtain a metal-modified carbon molecular sieve.

[0009] (3) Add 2,4,6-tris(2-imidopyrimidine-5-carboxylic acid)-1,3,5-s-triazine to distilled water, stir, then add metal-modified carbon molecular sieve, stir to perform surface modification, filter, wash with water, and dry to obtain a carbon molecular sieve for screening and separating nitrogen and hydrogen.

[0010] Furthermore, the mass ratio of the metal salt compound to the biomass carbon source is (0.01-0.018): 1. The biomass carbon source is palm shell, olive shell, coconut shell, rice or coffee grounds.

[0011] Furthermore, the treatment method in (1) is: mixing the metal salt compound with the biomass carbon source, grinding them evenly, and obtaining the metal-treated biomass carbon source.

[0012] Furthermore, the treatment method in (1) is: mixing the metal salt compound with the biomass carbon source, placing in a reactor, heating to 220-240° C., heat treating for 2-4 hours, cooling, and obtaining a metal-treated biomass carbon source.

[0013] Furthermore, the treatment method in (1) is: adding the metal salt compound to distilled water, stirring, then adding the biomass carbon source, stirring for 36-48 hours, drying to remove moisture, and obtaining the metal-treated biomass carbon source.

[0014] Furthermore, the metal salt compound is an iron salt, a copper salt or a zinc salt; the iron salt includes ferric chloride; the copper salt includes copper chloride; the zinc salt includes zinc chloride.

[0015] Furthermore, in (2), the specific gas is any one or a combination of nitrogen, argon, and air, the pyrolysis temperature is 200-500°C, and the pyrolysis time is 1-2h; the inert gas is any one or a combination of nitrogen, argon, and helium, the activation temperature is 500-1000°C, and the activation time is 1-2h.

[0016] Furthermore, in (3), the surface modification temperature is 20-60°C and the time is 6-18h.

[0017] Furthermore, in (3), the mass ratio of 2,4,6-tris(2-imidopyrimidine-5-carboxylic acid)-1,3,5-s-triazine and the metal-modified carbon molecular sieve is (0.2-0.6):1.

[0018] Further, the preparation method of 2,4,6-tris (2-iminopyrimidine-5-carboxylic acid)-1,3,5-s-triazine is as follows: add cyanuric chloride, 2-aminopyrimidine-5-carboxylic acid, and triethylamine in a mass ratio of 1: (2.3-2.4): (2.6-3) to tetrahydrofuran, heat to 60-65°C, condense and reflux for 12-18h, distill under reduced pressure, wash with petroleum ether, and then recrystallize in ethanol to obtain 2,4,6-tris (2-iminopyrimidine-5-carboxylic acid)-1,3,5-s-triazine. The structural formula is:

[0019] .

[0020] The technical effect of the present invention is as follows: the present invention uses environmentally friendly and pollution-free olive shells, coconut shells, palm shells and the like as green biomass resources as carbon sources, utilizes metal salts such as ferric chloride, copper chloride, zinc chloride and the like to process the biomass carbon sources, and during high-temperature pyrolysis, generates metal nanoparticles such as iron and copper in the carbon molecular sieve; during pyrolysis and carbonization, the metal nanoparticles catalyze the carbonization of the biomass carbon source, thereby enhancing the carbonization of the carbon source, which is beneficial to improving the residual carbon content of the biomass carbon source and the utilization rate of biomass resources.

[0021] The present invention introduces nano-metal particles such as zinc, iron, and copper into the carbon molecular sieve as hydrogen absorption sites, which have certain adsorption properties for hydrogen and are beneficial to improving the adsorption capacity of the carbon molecular sieve for hydrogen. The metal-modified carbon molecular sieve is surface-modified by using 2,4,6-tris(2-iminopyrimidine-5-carboxylic acid)-1,3,5-s-triazine, which contains multiple triazine, pyrimidine nitrogen-containing groups, and carboxyl groups, and can coordinate and complex with nano-metal particles such as zinc, iron, and copper in the carbon molecular sieve, so that 2,4,6-tris(2-iminopyrimidine-5-carboxylic acid)-1,3,5-s-triazine is uniformly modified on the surface of the carbon molecular sieve, and a large number of active groups such as carboxyl and triazine are introduced on the surface, which has a strong interface interaction with hydrogen, and further improves the adsorption capacity of the carbon molecular sieve for hydrogen. The obtained carbon molecular sieve has almost no adsorption capacity for nitrogen, and the adsorption rate of hydrogen reaches 6.27-7.06mmol / g under a pressure of 1bra. It shows good effects of adsorbing hydrogen and screening and separating nitrogen and hydrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is the adsorption isotherm of hydrogen and nitrogen by the carbon molecular sieve used for screening and separating nitrogen and hydrogen in Example 1.

[0023] Figure 2 It is the adsorption isotherm of hydrogen and nitrogen by the carbon molecular sieve used for screening and separating nitrogen and hydrogen in Example 2.

[0024] Figure 3 It is the adsorption isotherm of hydrogen and nitrogen by the carbon molecular sieve used for screening and separating nitrogen and hydrogen in Example 3.

[0025] Figure 4 It is the adsorption isotherm of the carbon molecular sieve of comparative example 1 to hydrogen and nitrogen.

[0026] Figure 5 It is the adsorption isotherm of the metal-modified carbon molecular sieve of Comparative Example 2 to hydrogen and nitrogen.

[0027] Figure 6 It is the adsorption isotherm of hydrogen and nitrogen by the carbon molecular sieve used for screening and separating nitrogen and hydrogen in Comparative Example 3.

[0028] Figure 7 It is the adsorption isotherm of the carbon molecular sieve of Comparative Example 4 to hydrogen and nitrogen. DETAILED DESCRIPTION

[0029] For ease of understanding of the present invention, preferred embodiments of the present invention are provided below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0030] The implementation method is as follows:

[0031] The preparation method of the metal-treated biomass carbon source is as follows: mixing a metal salt compound with a biomass carbon source in a mass ratio of (0.01-0.018):1, wherein the metal salt compound is an iron salt, a copper salt or a zinc salt; the iron salt includes ferric chloride, the copper salt includes copper chloride, and the zinc salt includes zinc chloride; grinding evenly to obtain the metal-treated biomass carbon source.

[0032] The preparation method of the metal-treated biomass carbon source is as follows: mixing a metal salt compound with a biomass carbon source in a mass ratio of (0.01-0.018):1, wherein the metal salt compound is an iron salt, a copper salt or a zinc salt; the iron salt includes ferric chloride, the copper salt includes copper chloride, and the zinc salt includes zinc chloride; placing in a reaction kettle, heating to 220-240°C, heat treating for 2-4 hours, cooling, and obtaining the metal-treated biomass carbon source.

[0033] The preparation method of the metal-treated biomass carbon source is as follows: adding a metal salt compound to distilled water, stirring and then adding the biomass carbon source, controlling the mass ratio of the metal salt compound to the biomass carbon source to be (0.01-0.018):1, wherein the metal salt compound is an iron salt, a copper salt or a zinc salt; the iron salt includes ferric chloride, the copper salt includes copper chloride, and the zinc salt includes zinc chloride; stirring for 36-48 hours, drying to remove moisture, and obtaining the metal-treated biomass carbon source.

[0034] The preparation method of 2,4,6-tris(2-iminopyrimidine-5-carboxylic acid)-1,3,5-s-triazine is as follows: add cyanuric chloride, 2-aminopyrimidine-5-carboxylic acid and triethylamine in a mass ratio of 1:(2.3-2.4):(2.6-3) to tetrahydrofuran, heat to 60-65°C, condense and reflux for 12-18h, distill under reduced pressure, wash with petroleum ether, and then recrystallize in ethanol to obtain 2,4,6-tris(2-iminopyrimidine-5-carboxylic acid)-1,3,5-s-triazine. The preparation reaction formula is:

[0035] .

[0036] The preparation method of the carbon molecular sieve used for screening and separating nitrogen and hydrogen is as follows:

[0037] (1) The metal-treated biomass carbon source is placed in a tubular furnace and pyrolyzed at 200-500°C for 1-2 hours in an atmosphere of any one or a combination of nitrogen, argon, and air; then activated at 500-1000°C for 1-2 hours in an atmosphere of any one or a combination of nitrogen, argon, and helium to obtain a metal-modified carbon molecular sieve.

[0038] (2) Add 20-60 g of 2,4,6-tris(2-imidopyrimidine-5-carboxylic acid)-1,3,5-s-triazine to distilled water, stir, then add 100 g of metal-modified carbon molecular sieve, stir at 20-60° C. for surface modification for 6-18 h, filter, wash with water, and dry to obtain a carbon molecular sieve for screening and separating nitrogen and hydrogen.

[0039] Example 1

[0040] (1) Using olive shell as a biomass carbon source, 6.2 g of zinc chloride was mixed with 500 g of crushed olive shell, placed in a reactor, heated to 230 °C, heat treated for 3 h, and cooled to obtain a metal-treated biomass carbon source.

[0041] (2) Place the metal-treated biomass carbon source in a tubular furnace, heat it to 500°C at a heating rate of 10°C / min in an argon atmosphere, and perform pyrolysis for 1 hour; then continue to heat it to 600°C for activation for 2 hours to obtain a metal-modified carbon molecular sieve. Observe the morphology, weigh it, and calculate the residual carbon content R. R = (mass of metal-modified carbon molecular sieve) / (mass of metal-treated biomass carbon source) × 100%.

[0042] (3) Add 8 g of cyanuric chloride, 19.2 g of 2-aminopyrimidine-5-carboxylic acid and 20.8 g of triethylamine to 150 mL of tetrahydrofuran, heat to 60 °C, condense and reflux for 18 h, distill under reduced pressure, wash with petroleum ether, and then recrystallize from ethanol to obtain 2,4,6-tris(2-iminopyrimidine-5-carboxylic acid)-1,3,5-s-triazine.

[0043] (4) Add 35 g of 2,4,6-tris(2-imidopyrimidine-5-carboxylic acid)-1,3,5-s-triazine to 1.5 L of distilled water, stir, then add 100 g of metal-modified carbon molecular sieve, stir at 30 °C for 18 h for surface modification, filter, wash with water, and dry to obtain a carbon molecular sieve for sieving and separating nitrogen and hydrogen.

[0044] Example 2

[0045] (1) Using coconut shell as a biomass carbon source, add 9 g of ferric chloride into 500 mL of distilled water, stir, then add 500 g of crushed coconut shell, stir for 48 h, dry to remove moisture, and obtain a metal-treated biomass carbon source.

[0046] (2) Place the metal-treated biomass carbon source in a tubular furnace, heat it to 350°C at a heating rate of 10°C / min in an argon atmosphere, and perform pyrolysis for 2 hours; then continue to heat it to 500°C in an argon and helium atmosphere with a volume ratio of 1:1 for 1 hour to obtain a metal-modified carbon molecular sieve. Observe the morphology, weigh it, and calculate the residual carbon content R. R = (mass of metal-modified carbon molecular sieve) / (mass of metal-treated biomass carbon source) × 100%.

[0047] (3) Add 8 g of cyanuric chloride, 18.4 g of 2-aminopyrimidine-5-carboxylic acid and 22.4 g of triethylamine to 150 mL of tetrahydrofuran, heat to 60 °C, condense and reflux for 18 h, distill under reduced pressure, wash with petroleum ether, and then recrystallize from ethanol to obtain 2,4,6-tris(2-iminopyrimidine-5-carboxylic acid)-1,3,5-s-triazine.

[0048] (4) Add 60 g of 2,4,6-tris(2-imidopyrimidine-5-carboxylic acid)-1,3,5-s-triazine to 1.5 L of distilled water, stir, then add 100 g of metal-modified carbon molecular sieve, stir at 20°C for 18 h for surface modification, filter, wash with water, and dry to obtain a carbon molecular sieve for screening and separating nitrogen and hydrogen.

[0049] Example 3

[0050] (1) Using palm shell as a biomass carbon source, 5 g of copper chloride was mixed with 500 g of crushed palm shell and ground evenly to obtain a metal-treated biomass carbon source.

[0051] (2) Place the metal-treated biomass carbon source in a tubular furnace, heat it to 200°C at a heating rate of 5°C / min in an air atmosphere, and pyrolyze it for 2 hours; then heat it to 1000°C in a nitrogen atmosphere and activate it for 1 hour to obtain a metal-modified carbon molecular sieve. Observe the morphology, weigh it, and calculate the residual carbon content R. R = (mass of metal-modified carbon molecular sieve) / (mass of metal-treated biomass carbon source) × 100%.

[0052] (3) Add 8 g of cyanuric chloride, 19.2 g of 2-aminopyrimidine-5-carboxylic acid and 24 g of triethylamine to 200 mL of tetrahydrofuran, heat to 65 °C, condense and reflux for 12 h, distill under reduced pressure, wash with petroleum ether, and then recrystallize from ethanol to obtain 2,4,6-tris(2-iminopyrimidine-5-carboxylic acid)-1,3,5-s-triazine.

[0053] (4) Add 20 g of 2,4,6-tris(2-imidopyrimidine-5-carboxylic acid)-1,3,5-triazine to 1 L of distilled water, stir, then add 100 g of metal-modified carbon molecular sieve, stir at 60 °C for 6 h for surface modification, filter, wash with water, and dry to obtain a carbon molecular sieve for sieving and separating nitrogen and hydrogen.

[0054] Comparative Example 1

[0055] (1) Olive shells were used as biomass carbon sources. After crushing, they were placed in a tube furnace and heated to 500°C at a heating rate of 10°C / min in an argon atmosphere for 1 hour. The temperature was then raised to 600°C for activation for 2 hours to obtain a carbon molecular sieve. The morphology was observed, the weight was weighed, and the residual carbon content R was calculated. R = (mass of carbon molecular sieve) / (mass of biomass carbon source) × 100%.

[0056] Comparative Example 2

[0057] (1) Using olive shell as a biomass carbon source, 6.2 g of zinc chloride was mixed with 500 g of crushed olive shell, placed in a reactor, heated to 230 °C, heat treated for 3 h, and cooled to obtain a metal-treated biomass carbon source.

[0058] (2) Place the metal-treated biomass carbon source in a tubular furnace, heat it to 500°C at a heating rate of 10°C / min in an argon atmosphere, and perform pyrolysis for 1 hour; then continue to heat it to 600°C for activation for 2 hours to obtain a metal-modified carbon molecular sieve. Observe the morphology, weigh it, and calculate the residual carbon content R. R = (mass of metal-modified carbon molecular sieve) / (mass of metal-treated biomass carbon source) × 100%.

[0059] Comparative Example 3

[0060] (1) Olive shells were used as biomass carbon sources. After crushing, they were placed in a tube furnace and heated to 500°C at a heating rate of 10°C / min in an argon atmosphere for 1 hour. The temperature was then raised to 600°C for activation for 2 hours to obtain a carbon molecular sieve. The morphology was observed, the weight was weighed, and the residual carbon content R was calculated. R = (mass of carbon molecular sieve) / (mass of biomass carbon source) × 100%.

[0061] (2) Add 35 g of 2,4,6-tris(2-imidopyrimidine-5-carboxylic acid)-1,3,5-s-triazine (prepared according to the method of Example 1) to 1.5 L of distilled water, stir, then add 100 g of metal-modified carbon molecular sieve, stir at 30° C. for surface modification for 18 h, filter, wash with water, and dry to obtain a carbon molecular sieve for sieving and separating nitrogen and hydrogen.

[0062] Comparative Example 4

[0063] (1) Asphalt was used as the carbon source. 10 g of asphalt was added to 300 mL of carbon tetrachloride, and then 60 g of potassium hydroxide was added. After thorough mixing, the carbon tetrachloride was removed by vacuum distillation. The material was placed in a tubular furnace and heated to 300 °C at a heating rate of 5 °C / min in a nitrogen atmosphere. The temperature was pyrolyzed for 1 h, and then the temperature was continued to be raised to 700 °C and activated for 1 h to obtain a carbon molecular sieve. The morphology was observed, the weight was weighed, and the residual carbon content R was calculated. R = (mass of carbon molecular sieve) / (mass of carbon source) × 100%.

[0064] The test results of morphology and carbon residue are shown in Table 1.

[0065] Table 1 Carbon molecular sieve morphology and residual carbon content test

[0066]

[0067] As can be seen from Table 1, the residual carbon content of the metal-modified carbon molecular sieves of Examples 1, 2, 3 and Comparative Example 2 reaches 27.82-31.54%. It may be that the added zinc chloride and ferric chloride generate metal nanoparticles at high temperature, which catalyze the carbonization of biomass carbon sources such as olive shells and coconut shells during pyrolysis and carbonization, thereby enhancing the carbonization of the carbon source, which is beneficial to improving the residual carbon content of the biomass carbon source and the utilization rate of biomass resources.

[0068] Comparative Examples 1 and 3 used olive shell as the biomass carbon source without zinc chloride treatment. The residual carbon content of the obtained carbon molecular sieves was 25.33-25.36%, which was lower than that of Example 1.

[0069] In comparative example 4, asphalt is used as the carbon source, and the residual carbon content is only 15.21%.

[0070] Adsorption isotherm test method:

[0071] The 3-Flex model full-function multi-purpose analyzer manufactured by Micrometrics of the United States was used to determine the adsorption amount of hydrogen and nitrogen by the material at -195℃ and different pressures by the volume method, and then the single-component adsorption isotherms of hydrogen and nitrogen were obtained. The specific experimental steps are as follows: Take a clean and dry 3-Flex test tube and accurately weigh the empty tube mass M0. Add 80 mg of the sample to be tested into the test tube and vacuum degas for 6 h at 150℃. After the sample tube and sample are cooled to room temperature, accurately weigh the total mass of the sample and the empty tube M1, and the mass of the test sample is M1-M0. Install the vacuum degassed sample and sample tube on the instrument, enter the mass data such as M0 and M1 in the 3-Flex software, and establish a test program according to the pressure range. Run the test program, and the instrument completes the determination of the adsorption isotherm. The test temperature is precisely controlled by a Dewar flask filled with liquid nitrogen.

[0072] Test results see Figure 1-Figure 7 .

[0073] Depend on Figures 1 to 3 It is shown that the carbon molecular sieves used for screening and separating nitrogen and hydrogen in Examples 1-3 have almost no adsorption capacity for nitrogen. At a pressure of 1 bra, the adsorption rates for hydrogen are 6.27 mmol / g, 7.06 mmol / g, and 6.77 mmol / g, respectively. It shows a good effect of adsorbing hydrogen and screening and separating nitrogen and hydrogen. This is because the biomass carbon source is treated with zinc chloride, copper chloride, and ferric chloride. During the high-temperature pyrolysis and activation process, nano-metal particles such as zinc, iron, and copper are introduced into the carbon molecular sieve as hydrogen absorption sites, which have certain adsorption properties for hydrogen and are beneficial to improve the adsorption capacity of the carbon molecular sieve for hydrogen; then the metal-modified carbon molecular sieve is surface-modified using 2,4,6-tris(2-iminopyrimidine-5-carboxylic acid)-1,3,5-isotriazine, and 2,4,6-tris(2-iminopyrimidine-5-carboxylic acid)-1,3,5-isotriazine. 2,4,6-tris(2-iminopyrimidine-5-carboxylic acid)-1,3,5-s-triazine contains multiple triazines, pyrimidine nitrogen-containing groups, and carboxyl groups, which can be coordinated and complexed with nano-metal particles such as zinc, iron, and copper in carbon molecular sieves, so that 2,4,6-tris(2-iminopyrimidine-5-carboxylic acid)-1,3,5-s-triazine is evenly modified on the surface of carbon molecular sieves, and a large number of active groups such as carboxyl groups and triazines are introduced, which has a strong interfacial interaction with hydrogen, further improving the adsorption capacity of carbon molecular sieves for hydrogen.

[0074] In Comparative Example 1, olive shell was used as the biomass carbon source, and it was not treated with zinc chloride metal salt. The obtained carbon molecular sieve was not surface modified with 2,4,6-tris(2-imidopyrimidine-5-carboxylic acid)-1,3,5-s-triazine, and the adsorption capacity of hydrogen was only 3.51 mmol / g.

[0075] The olive shell biomass carbon source of Comparative Example 2 was treated with zinc chloride metal salt, but the obtained carbon molecular sieve was not surface modified with 2,4,6-tris(2-imidopyrimidine-5-carboxylic acid)-1,3,5-s-triazine, and the adsorption capacity of hydrogen was 4.13 mmol / g.

[0076] The olive shell biomass carbon source of Comparative Example 3 has not been treated with zinc chloride metal salt, and the carbon molecular sieve does not contain zinc metal nanoparticles. The carbon molecular sieve cannot coordinate and complex 2,4,6-tris(2-imidopyrimidine-5-carboxylic acid)-1,3,5-s-triazine, resulting in a low interfacial force between 2,4,6-tris(2-imidopyrimidine-5-carboxylic acid)-1,3,5-s-triazine and the carbon molecular sieve, and the surface modification effect of the carbon molecular sieve is poor. A large number of active groups such as carboxyl and triazine are not well introduced on the surface of the carbon molecular sieve. The adsorption capacity of the carbon molecular sieve for hydrogen is 4.78 mmol / g.

[0077] In Comparative Example 4, asphalt is used as the carbon source, and the obtained carbon molecular sieve has a high adsorption capacity for nitrogen, but has no adsorption performance for hydrogen.

Claims

1. A green preparation method of a carbon molecular sieve for screening and separating nitrogen and hydrogen, characterized in that: The preparation method comprises: (1) treating a biomass carbon source with a metal salt compound to obtain a metal-treated biomass carbon source; (2) placing the metal-treated biomass carbon source in a tubular furnace, pyrolyzing it in a specific gas atmosphere, and then activating it in an inert gas atmosphere to obtain a metal-modified carbon molecular sieve; (3) Add 2,4,6-tris(2-imidopyrimidine-5-carboxylic acid)-1,3,5-s-triazine to distilled water, stir, add metal-modified carbon molecular sieve, stir to perform surface modification, filter, wash with water, and dry to obtain a carbon molecular sieve for screening and separating nitrogen and hydrogen; The structural formula of the 2,4,6-tris(2-iminopyrimidine-5-carboxylic acid)-1,3,5-s-triazine is: 。 2. The green preparation method of carbon molecular sieve for screening and separating nitrogen and hydrogen according to claim 1, characterized in that: The mass ratio of the metal salt compound to the biomass carbon source is (0.01-0.018):1; the biomass carbon source is palm shell, olive shell, coconut shell, rice or coffee grounds.

3. The green preparation method of carbon molecular sieve for screening and separating nitrogen and hydrogen according to claim 1, characterized in that: The treatment method in (1) is: mixing the metal salt compound with the biomass carbon source, grinding them evenly, and obtaining the metal-treated biomass carbon source.

4. The green preparation method of carbon molecular sieve for screening and separating nitrogen and hydrogen according to claim 1, characterized in that: The treatment method in (1) is as follows: mixing the metal salt compound with the biomass carbon source, placing the mixture in a reaction kettle, heating the mixture to 220-240° C., heat treating the mixture for 2-4 hours, and cooling the mixture to obtain the metal-treated biomass carbon source.

5. The green preparation method of carbon molecular sieve for screening and separating nitrogen and hydrogen according to claim 1, characterized in that: The treatment method in (1) is as follows: adding a metal salt compound to distilled water, stirring, then adding a biomass carbon source, stirring for 36-48 hours, drying to remove moisture, and obtaining a metal-treated biomass carbon source.

6. The green preparation method of the carbon molecular sieve for screening and separating nitrogen and hydrogen according to any one of claims 1 to 5, characterized in that: The metal salt compound is an iron salt, a copper salt or a zinc salt; the iron salt includes ferric chloride, the copper salt includes copper chloride, and the zinc salt includes zinc chloride.

7. The green preparation method of carbon molecular sieve for screening and separating nitrogen and hydrogen according to claim 1, characterized in that: In (2), the specific gas is any one or a combination of nitrogen, argon, and air, the pyrolysis temperature is 200-500°C, and the pyrolysis time is 1-2h; the inert gas is any one or a combination of nitrogen, argon, and helium, the activation temperature is 500-1000°C, and the activation time is 1-2h.

8. The green preparation method of carbon molecular sieve for screening and separating nitrogen and hydrogen according to claim 1, characterized in that: In the above (3), the temperature during surface modification is 20-60°C and the time is 6-18h.

9. The green preparation method of carbon molecular sieve for screening and separating nitrogen and hydrogen according to claim 1, characterized in that: In the above (3), the mass ratio of 2,4,6-tris(2-iminopyrimidine-5-carboxylic acid)-1,3,5-s-triazine to the metal-modified carbon molecular sieve is (0.2-0.6):

1.

10. The green preparation method of carbon molecular sieve for screening and separating nitrogen and hydrogen according to claim 9, characterized in that: The preparation method of 2,4,6-tris(2-iminopyrimidine-5-carboxylic acid)-1,3,5-s-triazine is as follows: adding cyanuric chloride, 2-aminopyrimidine-5-carboxylic acid and triethylamine in a mass ratio of 1:(2.3-2.4):(2.6-3) to tetrahydrofuran, heating to 60-65° C., condensing and refluxing for 12-18 hours, distilling under reduced pressure, washing with petroleum ether, and then recrystallizing in ethanol to obtain 2,4,6-tris(2-iminopyrimidine-5-carboxylic acid)-1,3,5-s-triazine.

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