A nitrous oxide capture and separation adsorbent and its preparation method and application

Abstract

The present invention discloses an adsorbent for capturing and separating nitrous oxide, and its preparation method and application. The preparation method comprises: adding an acid anhydride compound, a polyamine compound, a crosslinking agent, and a catalyst to a reaction solvent under a protective gas atmosphere to carry out a reaction; obtaining a precipitate after the reaction is completed, separating, washing, and drying to obtain the adsorbent for capturing and separating nitrous oxide; the acid anhydride compound is a compound containing two or more carboxylic anhydride functional groups; the polyamine compound is a compound containing two or more NH2 functional groups; the crosslinking agent is triaminopyrimidine; and the catalyst is isoquinoline. The present invention uses an acid anhydride compound, a polyamine compound, and triaminopyrimidine as raw materials, and crosslinks and polymerizes them through an imidization reaction. The reaction conditions are simple and easy to control, the cost of the reaction raw materials is low, and an adsorbent with different pore structures can be produced. The adsorbent can capture and separate N2O from mixed gases by simple, low-consumption, and high-efficiency pressure swing adsorption.

Description

Technical Field

[0001] The present invention relates to the technical field of greenhouse gas capture and separation, and in particular to a nitrous oxide capture and separation adsorbent, a preparation method and an application thereof. Background Art

[0002] The three major greenhouse gases are CO2, CH4, and N2O. As the third most important greenhouse gas, N2O, also known as nitrous oxide, has undoubtedly contributed significantly to global warming. It also has the potential to contribute to the ozone hole, thereby increasing ultraviolet radiation. N2O not only affects the atmosphere, but also forms nitrates when dissolved in the atmosphere. These nitrates enter water bodies through rainfall and other means, leading to eutrophication and impacting the balance of aquatic ecosystems. N2O already exists at certain concentrations in the atmosphere, and its levels are increasing annually due to human industrial activities. While N2O can negatively impact the atmospheric environment, high-purity N2O has practical applications in many areas of life, such as healthcare, electronics, and food. Therefore, recovering and utilizing N2O is an optimal option from both an environmental and economic perspective.

[0003] N2O is primarily emitted from natural sources and anthropogenic activities, with agriculture, industry, and other sources contributing to as much as 40% of total N2O emissions. Current industrial activities require more than simply reducing N2O emissions; treatment is also necessary. Treatment of N2O from adipic acid or nitric acid production exhaust typically involves the following methods: 1) decomposition, which breaks down N2O into non-greenhouse gases N2 and O2. However, this method requires demanding operating conditions and catalysts, is energy-intensive, and is environmentally unfriendly. 2) Direct use of N2O as an oxidant, such as the one-step oxidation of benzene to phenol. This method obviously requires high-purity N2O. Therefore, finding a low-energy, environmentally friendly method for capturing N2O is crucial.

[0004] Comparing numerous treatment methods, adsorption processes offer advantages such as relatively simple preparation, high efficiency, low energy consumption, and the ability to produce high-purity target gases, making them a more suitable method for separating N2O. Among these, pressure swing adsorption (PSA) for separating binary gas mixtures has received considerable attention in recent years. For PSA, the most important requirement is finding an adsorption separation material with excellent performance. Since the performance of the material directly affects the separation efficiency, purity of the target product, and sustainable operating time, the adsorption separation material is crucial for the industrialization of this technology. Among numerous adsorption materials, polyimides (PIs) offer significant advantages over molecular sieves and activated carbon, with superior overall performance. They possess excellent thermal stability, mechanical properties, a rich pore structure, adjustable pore size, and the ability to be functionalized, demonstrating significant potential for gas adsorption separation.

[0005] CN108837678A discloses a method for treating nitrogen oxide waste gas, which includes enrichment treatment of NOx waste gas and SCR treatment of NOx waste gas. The enrichment treatment includes the following steps: preparing an aqueous solution of glycidyl ether in a soaking container, placing a filler plate made of polyimide in the soaking container, and drying it at 75-85°C to obtain an enrichment filler; placing the enrichment filler in the pipeline for discharging waste gas, and the cross-section of the enrichment filler is equal to the cross-section of the pipeline for discharging waste gas; during SCR treatment, placing the enrichment filler after enriching the waste gas in the SCR system for treatment; after the SCR treatment is completed, air is passed into the SCR reaction system to replace the gas, the polyimide filler plate is removed, the pH of the SCR reaction system is adjusted to 5.5, and FeCl3 and ethanol are added until the solid is completely precipitated, and the filtrate is filtered and dripped with NaOH aqueous solution until the solid is completely precipitated, so that the NOx waste gas can be enriched and then treated centrally. However, this method for treating nitrogen oxide waste gas has the following defects: (1) it uses aromatic diamine and aromatic tetracarboxylic acid dialkyl ester to prepare condensation-type aromatic polyimide, which is only used as a filler and soaked to be used as an enrichment filler. The enrichment filler uses Pd (palladium) precious metal, which is relatively expensive; (2) the entire treatment process is extremely complicated and energy-intensive.

[0006] For example, CN114191981A discloses a harmless treatment method for industrial waste gas, comprising the following steps: passing nitrogen oxide-containing flue gas through a dust removal device for dust removal to obtain dust-removed flue gas; passing the dust-removed flue gas through a desulfurization device for desulfurization to obtain desulfurized flue gas; adjusting the temperature of the desulfurized flue gas to 100-200°C, and then passing it through an SCR denitrification device equipped with a denitrification filter material, wherein the denitrification filter material is a polyimide fiber filter material covalently grafted with a denitrification catalyst; and passing ammonia gas into the SCR denitrification device for selective catalytic reduction denitrification, thereby completing the harmless treatment of the flue gas. However, this method has the following drawbacks: in the gas denitrification step, the heated gas is passed through a polyimide fiber filter material covalently grafted with a denitrification catalyst, which mainly involves catalyst preparation and denitrification via chemical reaction, but does not describe the selection of the polyimide.

[0007] For example, CN118028999A discloses a method for preparing high-performance polyimide fibers by two-step chemical imidization, which comprises the following steps: adding a certain amount of polyamino compound to a polyamic acid spinning solution prepared by the polycondensation reaction of dianhydride and diamine monomers to obtain a slightly cross-linked polyamic acid solution; adding a certain amount of imidization agent to the above polyamic acid solution to carry out a first imidization reaction to obtain a polyamic acid spinning solution with a certain degree of pre-imidization; according to a wet spinning process, the spinning solution is extruded through a spinneret and directly enters a coagulation bath composed of an imidization agent to carry out a second imidization reaction to obtain gelled nascent fibers, which are then subjected to high-multiple drafting at this stage; thereafter, partially imidized fibers are obtained after washing and drying; and finally, the polyimide fibers are obtained after further thermal cyclization and drafting. However, this method has the following defects: (1) its preparation method is to first prepare a slightly cross-linked polyamic acid solution, then add an imidization agent to obtain a pre-imidized polyamic acid spinning solution, and then perform a second imidization reaction to obtain gelled primary fibers. The preparation steps are numerous and complicated; (2) the cross-linking of the obtained polyimide fibers is not sufficient.

[0008] For example, CN111748113A discloses a heat-resistant low-dielectric-constant polyimide film, the raw materials of which include: diamine monomer, dianhydride monomer, 2,4,6-triaminopyrimidine, octa(aminophenyltrioxysilane) and modified nano-hollow silica, wherein the content of modified silica is 3.5-4.5wt%. The application also discloses a method for preparing the above-mentioned heat-resistant low-dielectric-constant polyimide film: in an inert gas atmosphere, the diamine monomer, 2,4,6-triaminopyrimidine, modified nano-hollow silica and N,N-dimethylacetamide are ultrasonically mixed, and then the dianhydride monomer is added to react at room temperature for 3-5 hours, and then octa(aminophenyltrioxysilane) is added to continue the reaction for 1-2 hours to obtain a glue solution; after degassing the glue solution, it is coated on the surface of a substrate, imidized, naturally cooled to room temperature, and demolded to obtain a heat-resistant low-dielectric-constant polyimide film. However, the preparation method of the polyimide film disclosed in the patent application has the following defects: (1) During its preparation process, it is necessary to first mix and prepare the glue solution, and then go through multiple steps of heating operations, etc., and the reaction steps are complicated; (2) The prepared material does not have N2O gas separation performance.

[0009] For example, "Designed synthesis of large-pore crystalline polyimide covalentorganic framework" (Qianrong Fang, Yushan Yan, et al., Nature Communications, Vol. 5, No. 1, p. 8) discloses the preparation of polyimide COFs (porous crystalline polymers) by imidization reaction of dianhydrides and triamines, with pore sizes as large as The specific surface area is as high as 2346m 2 / g, which is a relatively high level among amorphous porous polyimides and two-dimensional COFs. However, its reaction conditions are relatively harsh, energy consumption is high, the product cost is higher, and it is not easy to apply industrially.

[0010] Another example is "Effect of the Number of Methyl Groups in DMOF on N2O Adsorption and N2O / N2Separation" (Li Wang, Jiangfeng Yang et al., Inorganic Chemistry, Vol. 63, No. 25, pp. 11501-11505), which studied the adsorption of N2O by a series of DMOF (metal-organic framework) materials with different polarity and ligand methyl groups. Simulations demonstrated the key role of surface methyl groups in the preferential affinity for N2O. However, the preparation cost of these adsorption materials with metal-organic frameworks is high, making them difficult to manufacture industrially.

[0011] Therefore, providing a polyimide adsorbent with a simple preparation method, mild reaction conditions, low preparation cost, and the ability to effectively capture and separate N2O gas has become an urgent problem to be solved in the industry. Summary of the Invention

[0012] The present invention aims to provide an adsorbent for capturing and separating nitrous oxide, as well as its preparation method and application. This method utilizes an acid anhydride compound, a polyamine compound, and triaminopyrimidine as raw materials, and employs an imidization reaction for cross-linking polymerization. The reaction conditions are simple and easy to control, and the raw materials are low-cost. This polyimide adsorbent with varying pore structures can be produced. This adsorbent can be used as a nitrous oxide capture and separation adsorbent to capture and separate N2O from mixed gases using simple, low-cost, and highly efficient pressure swing adsorption.

[0013] In order to achieve the above objectives, the present invention adopts the following technical solutions:

[0014] The first aspect of the present invention provides a method for preparing a nitrous oxide capture and separation adsorbent, comprising the following steps:

[0015] Under a protective gas atmosphere, an acid anhydride compound, a polyamine compound, a cross-linking agent and a catalyst are added to a reaction solvent to carry out a reaction; after the reaction is completed, a precipitate is obtained, which is separated, washed and dried to obtain a polyimide adsorbent, i.e., a nitrous oxide capture and separation adsorbent;

[0016] The acid anhydride compound is a compound containing two or more carboxylic anhydride functional groups; the polyamine compound is a compound containing two or more NH2 functional groups; the cross-linking agent is triaminopyrimidine; and the catalyst is isoquinoline.

[0017] According to the preparation method of the present invention, preferably, the acid anhydride compound is selected from one or a combination of two or more of 1,4,5,8-naphthalenetetracarboxylic anhydride (NTCDA), pyromellitic dianhydride (PMDA), 3,4,9,10-perylenetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 4,4'-oxydiphthalic anhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), 1,2,3,4-butanetetracarboxylic dianhydride, mellitic acid trianhydride, terphenylene [2,3-c:6,7-c':10,11-c") trifuran-1,3,6,8,11,13-hexaone or hexaazatrimellitic acid trianhydride; wherein the combined acid anhydride compounds can be mixed in any proportion.

[0018] Specifically, the structural formulas corresponding to the above acid anhydride compounds are as follows:

[0019]

[0020]

[0021] More preferably, the acid anhydride compound is selected from one or a combination of two or more of mellitic acid trianhydride, terphenylene [2,3-c:6,7-c':10,11-c") trifuran-1,3,6,8,11,13-hexaone or hexaazatrimellitic acid trianhydride; wherein the combined acid anhydride compounds can be mixed in any proportion.

[0022] In the present invention, the more carboxylic anhydride functional groups in the acid anhydride compound, the greater the N2O adsorption capacity of the synthesized adsorbent; the more nitrogen atoms in the acid anhydride compound, the greater the N2O adsorption capacity of the synthesized adsorbent.

[0023] According to the preparation method of the present invention, preferably, the polyamine compound is selected from one or a combination of two or more of benzidine, tris(4-aminophenyl)amine (TAPA), 1,3,5-tris(4-aminophenyl)benzene (TAPB), 3,3'-diaminobenzidine, 4',5'-bis(4-aminophenyl)-[1,1':2',1"-terphenyl]-4,4"-diamine, tetrakis(4-aminophenyl)methane, N,N,N',N'-tetrakis(p-aminophenyl)-p-phenylenediamine, hexa(4-aminohexaphenyl)benzene, 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, and 4',4"',4""'-(1,3,5-triazine-2,4,6-triyl)tris(([1,1'-biphenyl]-4-amine)); wherein the combined polyamine compounds can be mixed in any proportion.

[0024] Specifically, the structural formulas of the above polyamine compounds are as follows:

[0025]

[0026]

[0027] More preferably, the polyamine compound is selected from one or a combination of tris(4-aminophenyl)amine (TAPA) and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine; wherein the combined polyamine compounds can be mixed in any proportion.

[0028] According to the preparation method of the present invention, preferably, the triaminopyrimidine is selected from one or a combination of two or more of 2,4,6-triaminopyrimidine (TAP), 4,5,6-triaminopyrimidine or 2,4,5-triaminopyrimidine; wherein the combined compounds can be mixed in any proportion.

[0029] Specifically, the structural formulas of the above triaminopyrimidines are as follows:

[0030]

[0031] According to the preparation method of the present invention, preferably, the reaction solvent is selected from one or a combination of two or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide, N-methylpyrrolidone (NMP), 1,3-dimethyl-2-imidazolidinone, 1,1,3-trimethylcyclohexenone, m-cresol, dodecane, diphenyl ether, cyclopentane, toluene, propylbenzene, mesitylene, and o-dichlorobenzene; wherein the combined reaction solvents can be mixed in any proportion.

[0032] According to the preparation method of the present invention, the reaction temperature is preferably 100-300°C and the reaction time is 24-200 hours. During the preparation process of the present invention, when the reaction temperature is higher than 300°C, the reaction product will decompose; when the reaction temperature is lower than 100°C, the reaction activation effect of the reactants cannot be achieved. The specific setting of the reaction temperature is determined by the boiling point of the reaction solvent to facilitate condensation reflux.

[0033] According to the preparation method of the present invention, preferably, the molar ratio of the total amount of the polyamine compound and the cross-linking agent to the acid anhydride is 1:(1-1.5);

[0034] The molar ratio of the polyamine compound to the cross-linking agent is 1:(0.3-3);

[0035] The molar ratio of the catalyst to the acid anhydride compound is (2.5-5):1.

[0036] The amount of the reaction solvent used needs to be sufficient to dissolve all the reactants. When all the reactants are dissolved, the amount of the solvent used has little effect on the reaction rate and yield. The protective gas is an inert gas commonly used in laboratories and nitrogen. Inert gases include helium, neon, argon, krypton, xenon, and radon.

[0037] According to the preparation method of the present invention, the separation adopts a separation method such as filtration and suction filtration to separate the precipitate generated in the reaction system; for example, normal pressure suction filtration, reduced pressure suction filtration, etc.

[0038] According to the preparation method of the present invention, preferably, the washing is performed with THF or THF and methanol, and is generally performed 3 to 5 times.

[0039] According to the preparation method of the present invention, preferably, the drying conditions include: vacuum drying at 80-110° C. for 24-72 hours.

[0040] In a preferred embodiment, the preparation method comprises:

[0041] First, a prepared reaction solvent is added to a pressure-resistant glass tube or other pressure-resistant container, followed by a mixture of an acid anhydride compound, a polyamine compound and triaminopyrimidine, and a catalyst, isoquinoline. The mixture is filled with inert gas for protection, the temperature is set at 100-300°C, and the reaction is carried out in a closed manner for 24-200 hours to obtain a precipitate; after separation, washing and drying, a cross-linked polyimide adsorbent, i.e., the nitrous oxide capture and separation adsorbent, is obtained.

[0042] The second aspect of the present invention provides a nitrous oxide capture and separation adsorbent obtained by any one of the above preparation methods.

[0043] A third aspect of the present invention provides the use of one or more nitrous oxide capture and separation adsorbents in capturing and separating N2O gas.

[0044] According to the application of the present invention, preferably, N2O gas is captured and separated from a mixed gas containing N2O; the mixed gas containing N2O is N2O / N2, N2O / H2 or N2O / CH4.

[0045] According to the application of the present invention, preferably, the temperature of the adsorption separation for capturing and separating the N2O gas is 298-313K, and the pressure of the adsorption separation is 0-4MPa.

[0046] According to the application of the present invention, preferably, the nitrous oxide capture and separation adsorbent is compounded with an ionic liquid.

[0047] According to the application of the present invention, preferably, the nitrous oxide capture and separation adsorbent and the ionic liquid are thoroughly mixed, dried, and then ground. The drying can be performed, for example, by vacuum drying at a temperature of 80 to 150°C. The drying time can be determined based on the specific drying effect, which is not limited by the present invention. After drying, the adsorbent and the ionic liquid are fully combined, and the grinding is performed after cooling to room temperature.

[0048] When the adsorbent synthesized by the present invention is compounded with an ionic liquid containing specific functional groups, such as a fluorine-containing ionic liquid or an amino-containing ionic liquid, the ionic liquid increases active sites and acts as a gel, thereby improving N₂O gas adsorption performance. More preferably, the ionic liquid is selected from one or a combination of two or more of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium hexafluorophosphate, and 1-aminopropyl-3-methylimidazolium bromide; the ionic liquids can be mixed in any proportion.

[0049] According to the application of the present invention, preferably, the mass ratio of the nitrous oxide capture and separation adsorbent to the ionic liquid is 95:5.

[0050] When using the nitrous oxide capture and separation adsorbent of the present invention to test gas adsorption performance, gas adsorption can be used under various conditions, such as pressure swing adsorption (PSA), temperature swing adsorption (TSA), and a combination of the two, pressure swing adsorption (PTSA).

[0051] In some embodiments, the temperature for the adsorption separation of the captured and separated N2O gas or the mixed gas containing N2O is set to 298K, and the pressure for the adsorption separation is set to 4MPa; wherein the adsorption amount of N2O of the synthesized material is 4.32~9.09mmol / g, and the separation selectivity of N2O / N2 is 10.50~100.82.

[0052] The beneficial effects of the present invention include:

[0053] 1) The nitrous oxide capture and separation adsorbent prepared by the present invention has a stable rigid structure, excellent thermal stability, and a rich and adjustable pore structure, and can quickly capture and separate the greenhouse gas nitrous oxide;

[0054] 2) The nitrous oxide capture and separation adsorbent of the present invention has low preparation cost, can be functionalized, and has mild synthesis conditions, and has the potential for industrial production;

[0055] 3) The process flow of the nitrous oxide capture and separation adsorbent prepared by the present invention for separating N2O mixed gas is simple, low in consumption, and high in efficiency. The target gas obtained is of high purity, which is of great significance for the separation, recovery and utilization of nitrous oxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 These are infrared spectra of products PI-1 to PI-3 prepared in Examples 1 to 3 of the present invention.

[0057] Figure 2 These are the thermogravimetric spectra of products PI-1 to PI-3 prepared in Examples 1 to 3 of the present invention.

[0058] Figure 3a This is the SEM image of the product PI-1 prepared in Example 1 of the present invention.

[0059] Figure 3b This is the SEM image of the product PI-2 prepared in Example 2 of the present invention.

[0060] Figure 3c This is the SEM image of the product PI-3 prepared in Example 3 of the present invention.

[0061] Figure 4 These are the XRD patterns of the products PI-1 to PI-3 prepared in Examples 1 to 3 of the present invention.

[0062] Figure 5aThis is the adsorption isotherm curve of N2O and N2 of the product PI-1 prepared in Example 1 of the present invention.

[0063] Figure 5b This is the adsorption isotherm curve of N2O and N2 of the product PI-2 prepared in Example 2 of the present invention.

[0064] Figure 5c This is the adsorption isotherm curve of N2O and N2 of the product PI-3 prepared in Example 3 of the present invention.

[0065] Figure 6 Schematic diagram of the adsorption selectivity of the product PI-1 prepared in Example 1 of the present invention for N2O / N2 mixed gas under different pressure conditions. DETAILED DESCRIPTION

[0066] In order to explain the present invention more clearly, the present invention is further described below in conjunction with preferred embodiments. Those skilled in the art should understand that the following specific description is illustrative rather than restrictive and should not be used to limit the scope of protection of the present invention.

[0067] All numerical specifications herein (e.g., temperatures, times, concentrations, and weights, including ranges for each thereof) are generally approximate and may be modified (+) or (-) in increments of 0.1 or 1.0. All numerical specifications are to be understood as being preceded by the term "about."

[0068] Example 1

[0069] This embodiment prepares a nitrous oxide capture and separation adsorbent PI-1, comprising the following steps:

[0070] In a 15 mL Pyrex test tube, 10 mL of a 1:1 volume ratio of mesitylene and N-methylpyrrolidone was added. Pyromellitic dianhydride (0.327 g, 1.5 mmol), tris(4-aminophenyl)amine (0.218 g, 0.75 mmol), and 2,4,6-triaminopyrimidine (0.0313 g, 0.25 mmol) were then added dropwise. 0.55 g of isoquinoline was then added dropwise. The Pyrex test tube was then filled with nitrogen and sealed. After sealing, the reaction mixture was heated at 150°C for 100 h to obtain a precipitate. This precipitate was isolated by suction filtration (using organic filter paper at atmospheric pressure) and washed three times with anhydrous THF and methanol. Finally, the solvent was removed by vacuum drying at 100°C to obtain PI-1 as a powder.

[0071] The reaction formula is as follows:

[0072]

[0073] Example 2

[0074] This embodiment prepares a nitrous oxide capture and separation adsorbent PI-2, comprising the following steps:

[0075] In a 15 mL Pyrex test tube, 10 mL of a 1:1 volume ratio of mesitylene and N-methylpyrrolidone was added. Pyromellitic dianhydride (0.327 g, 1.5 mmol), tris(4-aminophenyl)amine (0.145 g, 0.5 mmol), and 2,4,6-triaminopyrimidine (0.0626 g, 0.5 mmol) were then added dropwise. 0.55 g of isoquinoline was then added dropwise. The Pyrex test tube was then filled with nitrogen and sealed. After sealing, the reaction mixture was heated at 150°C for 100 h to obtain a precipitate. This precipitate was isolated by suction filtration (using organic filter paper at atmospheric pressure) and washed three times with anhydrous THF and methanol. Finally, the solvent was removed by vacuum drying at 100°C to obtain PI-2 as a powder.

[0076] The reaction formula is as follows:

[0077]

[0078] Example 3

[0079] This embodiment prepares a nitrous oxide capture and separation adsorbent PI-3, comprising the following steps:

[0080] In a 15 mL heat-resistant glass test tube, add 10 mL of a mixed solvent of mesitylene and N-methylpyrrolidone in a volume ratio of 1:1, add 0.327 g (1.5 mmol) of pyromellitic dianhydride, 0.0726 g (0.25 mmol) of tris(4-aminophenyl)amine, and 0.9385 g (0.75 mmol) of 2,4,6-triaminopyrimidine, and dropwise add 0.55 g of isoquinoline. The heat-resistant glass test tube is filled with nitrogen and sealed. After sealing, the reaction mixture is heated at 150°C for 100 h to obtain a precipitate. It is separated by suction filtration (normal pressure organic filter paper) and washed with anhydrous THF and methanol three times. Finally, the solvent is removed by vacuum drying at 100°C to obtain PI-3 in powder form. The reaction formula is as follows:

[0081]

[0082] Example 4

[0083] This embodiment prepares a nitrous oxide capture and separation adsorbent PI-4, comprising the following steps:

[0084] To a 15 mL Pyrex test tube, add 10 mL of a 1:1 volume ratio of toluene and N-methylpyrrolidone, 0.327 g (1.5 mmol) of pyromellitic dianhydride, 0.177 g (0.5 mmol) of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, and 0.0626 g (0.5 mmol) of 2,4,6-triaminopyrimidine. Add 0.55 g of isoquinoline dropwise. The Pyrex test tube is then filled with nitrogen and sealed. After sealing, the reaction mixture is heated at 100°C for 200 h to obtain a precipitate. This precipitate is isolated by suction filtration (atmospheric pressure organic filter paper) and washed three times with anhydrous THF and methanol. Finally, the solvent is removed by drying under vacuum at 80°C to obtain product PI-4.

[0085] The reaction formula is as follows:

[0086]

[0087] Example 5

[0088] This embodiment prepares a nitrous oxide capture and separation adsorbent PI-5, comprising the following steps:

[0089] To a 15 mL Pyrex test tube, a 1:1 volume ratio of mesitylene, N,N-dimethylformamide, and 1,3-dimethyl-2-imidazolidinone (10 mL) was added. 3,4,9,10-perylenetetracarboxylic dianhydride (0.588 g, 1.5 mmol), tris(4-aminophenyl)amine (0.145 g, 0.5 mmol), and 2,4,6-triaminopyrimidine (0.0626 g, 0.5 mmol) were added. 0.55 g of isoquinoline was added dropwise. The Pyrex test tube was filled with nitrogen and sealed. After sealing, the reaction mixture was heated at 300°C for 24 h to obtain a precipitate. This precipitate was isolated by suction filtration (atmospheric pressure organic filter paper) and washed three times with anhydrous THF and methanol. Finally, the solvent was removed by drying under vacuum at 100°C to obtain the product PI-5.

[0090] The reaction formula is as follows:

[0091]

[0092] Example 6

[0093] This embodiment prepares a nitrous oxide capture and separation adsorbent PI-6, comprising the following steps:

[0094] In a 15 mL Pyrex test tube, add 10 mL of a 1:1 volume ratio of mesitylene and N-methylpyrrolidone mixed solvent, 0.2881 g (1 mmol) of mellitic acid trianhydride, 0.145 g (0.5 mmol) of tris(4-aminophenyl)amine, and 0.0626 g (0.5 mmol) of 2,4,6-triaminopyrimidine. Add 0.55 g of isoquinoline dropwise. The Pyrex test tube is filled with nitrogen and sealed. After sealing, the reaction mixture is heated at 150°C for 100 h to obtain a precipitate. This precipitate is isolated by suction filtration (atmospheric pressure organic filter paper) and washed three times with anhydrous THF and methanol. Finally, the solvent is removed by vacuum drying at 100°C to obtain the product PI-6.

[0095] The reaction formula is as follows:

[0096]

[0097] Example 7

[0098] This embodiment prepares a nitrous oxide capture and separation adsorbent PI-7, comprising the following steps:

[0099] To a 15 mL Pyrex test tube, 10 mL of a 1:1 volume ratio of mesitylene and N-methylpyrrolidone was added. 0.4383 g (1 mmol) of terphenylene [2,3-c:6,7-c':10,11-c"]trifuran-1,3,6,8,11,13-hexaone, 0.145 g (0.5 mmol) of tris(4-aminophenyl)amine, and 0.0626 g (0.5 mmol) of 2,4,6-triaminopyrimidine were added dropwise. 0.55 g of isoquinoline was added dropwise. The Pyrex test tube was filled with nitrogen and sealed. After sealing, the reaction mixture was heated at 150°C for 100 h to obtain a precipitate, which was isolated by suction filtration (normal pressure organic filter paper) and washed with anhydrous THF and methanol three times. Finally, the solvent was removed by vacuum drying at 100°C to obtain the product PI-7.

[0100] The reaction formula is as follows:

[0101]

[0102] Example 8

[0103] This embodiment prepares a nitrous oxide capture and separation adsorbent PI-8, comprising the following steps:

[0104] To a 15 mL Pyrex test tube, add 10 mL of a 1:1 volume ratio of mesitylene and N-methylpyrrolidone mixed solvent, 0.4442 g (1 mmol) of hexaazatrimellitic trianhydride, 0.145 g (0.5 mmol) of tris(4-aminophenyl)amine, and 0.0626 g (0.5 mmol) of 2,4,6-triaminopyrimidine. Add 0.55 g of isoquinoline dropwise. The Pyrex test tube is filled with nitrogen and sealed. After sealing, the reaction mixture is heated at 150°C for 100 h to obtain a precipitate. This precipitate is isolated by suction filtration (atmospheric pressure organic filter paper) and washed three times with anhydrous THF and methanol. Finally, the solvent is removed by vacuum drying at 100°C to obtain the product PI-8.

[0105] The reaction formula is as follows:

[0106]

[0107] Example 9

[0108] This example uses the nitrous oxide capture and separation adsorbent PI-2 prepared in Example 2 and mixes it with 5% ILc to prepare the PI-9 adsorbent, including the following steps:

[0109] Weigh 0.95 g of PI-2 adsorbent powder and place it in a glass beaker. Weigh 0.05 g of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ionic liquid and slowly add it to the beaker. Stir the mixture and ultrasonicate for 30 minutes to mix thoroughly. Transfer the mixture to a vacuum drying oven and dry it under vacuum at 100°C for 4 hours to fully combine the two. After drying, remove the mixture and cool it to room temperature. Grind the compound to obtain PI-9 adsorbent.

[0110] (1) Test characterization

[0111] (1) Infrared (IR) test characterization

[0112] The present invention conducted infrared spectrum test on product PI-1, product PI-2 and product PI-3, and the infrared spectra thereof are as follows Figure 1 As shown, the products PI-1, PI-2 and PI-3 all showed the following peaks: 1780 cm -1 and 1720cm -1 The peaks near 1375 cm are attributed to the asymmetric and symmetric vibrations of the C=O group of the imine ring; -1 The peak near 725cm is caused by the tensile vibration of CNC; -1 The peaks near the imine are caused by the deformation of the imine. These infrared absorption peaks confirm that the material has been successfully imidized. At the same time, the obvious 3200 cm -1-3500cm -1 The characteristic peaks of amino groups within the range have completely disappeared in the cross-linked product, proving that the cross-linking reaction was successful and the product was successfully synthesized.

[0113] (2) Thermogravimetric (TG) test characterization

[0114] The present invention measured the TG curves of product PI-1, product PI-2 and product PI-3 at 25-800°C under N2 atmosphere. Figure 2 As shown, weightlessness can be divided into three stages:

[0115] The first temperature stage: 25-200℃. The temperature in this stage is not high. Due to the complex pores of the sample, some water and solvent remain in it. In this temperature stage, the three products remove the water molecules and the gas molecules remaining in the pores, resulting in a decrease in quality.

[0116] The second stage: 200-400°C. At this temperature stage, the three products lose weight slowly, which is mainly due to the removal of some high-boiling point organic solvents remaining in the three products.

[0117] The third stage: 400-800℃. In this temperature stage, all three products lose weight rapidly. It is the main weight loss stage in the entire thermogravimetric experiment. This stage is caused by the thermal decomposition of the three products. At the same time, the material pores of the three products begin to collapse in this stage.

[0118] It can be seen that product PI-1, product PI-2 and product PI-3 all have good thermal stability.

[0119] (3) Scanning electron microscope (SEM) test characterization

[0120] The surface structures of the products PI-1, PI-2 and PI-3 were observed by cold field emission scanning electron microscope. Figure 3a to Figure 3c As shown, although the surface morphologies of the three samples are different, they all show a rough surface and have a large number of particles. These characteristics indicate that this series of materials are suitable for use in the field of gas adsorption separation.

[0121] (4) X-ray diffraction (PXRD) test characterization

[0122] The present invention uses powder X-ray diffractometer to test the properties of product PI-1, product PI-2 and product PI-3, as shown in FIG. Figure 4 As shown, they all show the common diffuse "steamed bun peak", indicating that the synthesized materials are amorphous.

[0123] (2) Adsorption capacity test

[0124] (1) Pure gas adsorption test

[0125] The adsorption properties of products PI-1, PI-2, PI-3, PI-6, PI-7, PI-8 and PI-9 for gas N2O and gas N2 were measured at 298K in the pressure range of 0 to 4 MPa using a high-temperature and high-pressure adsorber analyzer (3H-2000PH, Beijing Best Instrument Technology Co., Ltd.). Tables 1 to 7 show the specific test data of the adsorption amounts of products PI-1, PI-2, PI-3, PI-6, PI-7, PI-8 and PI-9 for gas N2O and gas N2, respectively.

[0126] As can be seen from Tables 1 to 3, under essentially the same pressure conditions, the adsorption capacity of product PI-1 for N2O is 10 to 32 times that of N2. Under essentially the same pressure conditions, the adsorption capacity of product PI-2 for N2O is 8 to 29 times that of N2. Under essentially the same pressure conditions, the adsorption capacity of product PI-3 for N2O is 4 to 42 times that of N2. This shows that the adsorption effect of this series of materials on N2O is far superior to that on N2.

[0127] The adsorption isotherms of products PI-1, PI-2 and PI-3 for pure gas N2O and gas N2 are as follows: Figure 5a 、 Figure 5b as well as Figure 5c As shown in the figure, it can be seen that at 4 MPa, the products PI-1, PI-2 and PI-3 all show huge differences in the adsorption capacity of N2O / N2, and the adsorption capacity of gas N2O is 9 to 11 times that of gas N2. This shows that the products PI-1, PI-2 and PI-3 all have excellent N2O / N2 separation capabilities, that is, they have good separation performance for gas N2O.

[0128] Tables 1-7 show significant differences in the adsorption capacities of products PI-2, PI-6, PI-7, PI-8, and PI-9. At 298 K and a pressure of 4 MPa, the adsorption capacities of products PI-2, PI-6, PI-7, PI-8, and PI-9 reached 6.93 mmol / g, 7.48 mmol / g, 7.18 mmol / g, 8.60 mmol / g, and 9.09 mmol / g, respectively. Their adsorption capacities for N₂O were 0.74 mmol / g, 0.89 mmol / g, 0.67 mmol / g, 0.70 mmol / g, and 0.94 mmol / g, respectively. This indicates that the N₂O adsorption capacities of products PI-2, PI-6, PI-7, PI-8, and PI-9 were consistently higher than those for N₂O, indicating that the adsorption affinities of products PI-2, PI-6, PI-7, PI-8, and PI-9 for N₂O were significantly stronger than those for N₂O. The order of N₂O adsorption capacity is PI-9 > PI-8 > PI-6 > PI-7 > PI-2. This indicates that the greater the number of functional groups in the anhydride, the greater the N₂O adsorption capacity of the synthesized adsorbent, and the greater the nitrogen atom content in the anhydride, the greater the N₂O adsorption capacity of the synthesized adsorbent. Furthermore, compounding the adsorbent with a fluorine-containing ionic liquid can improve N₂O gas adsorption performance.

[0129] Table 1 Measured adsorption capacity of N2O and N2 by product PI-1 at the highest pressure of 4 MPa

[0130]

[0131] Table 2 Measured adsorption capacity of product PI-2 for N2O and N2 at the highest pressure of 4MPa

[0132]

[0133] Table 3 Measured adsorption capacity of product PI-3 for N2O and N2 at the highest pressure of 4MPa

[0134]

[0135] Table 4 Measured adsorption capacity of product PI-6 for N2O and N2 at the highest pressure of 4MPa

[0136]

[0137]

[0138] Table 5 Measured adsorption capacity of product PI-7 for N2O and N2 at the highest pressure of 4MPa

[0139]

[0140] Table 6 Measured adsorption capacity of N2O and N2 by product PI-8 at the highest pressure of 4MPa

[0141]

[0142] Table 7 Measured adsorption capacity of product PI-9 for N2O and N2 at the highest pressure of 4MPa

[0143]

[0144]

[0145] (2) Analysis of the effects of products PI-1, PI-2, PI-6, PI-7, PI-8, and PI-9 on N2O / N2 selectivity

[0146] The Langmuir equation was used to fit the adsorption isotherms of products PI-1, PI-2, PI-6, PI-7, PI-8, and PI-9, where the Langmuir equation is:

[0147]

[0148] Where: q—equilibrium adsorption capacity per unit volume (mmol / g), q m —saturated adsorption capacity per unit volume of adsorbent (mmol / g), p—equilibrium pressure (MPa), b—Langmuir constant (MPa -1 The Langmuir model can be used to fit the experimental data to determine the separation selectivity of N2O and N2.

[0149] (3) Calculation of separation coefficient of product PI-1 at different pressures

[0150] The Langmuir adsorption model was adopted and the IAST method was used to calculate the separation coefficients of different PI products for binary mixed components (N2O and N2 mixture). In order to simulate the actual industrial production environment, the N2O / N2 ratio in adipic acid tail gas, that is, the binary mixed gas with an N2O content of 40%, was analyzed and the separation coefficients were calculated under different pressures.

[0151] First, using product PI-1, we calculated the variation of N2O / N2 selectivity with the molar ratio of gas components at three different pressures: 1MPa, 2MPa, and 4MPa. Figure 6As shown, the selectivity of N2O / N2 increases with the increase of N2O content in the mixed components, but the slopes of the three curves are different, indicating that at 4MPa, the selectivity increases fastest with the increase of N2O content in the components, followed by 2MPa, and the slowest at 1MPa. According to this rule, it can be seen that at higher pressures, with the increase of N2O mole fraction, the selectivity coefficient increases faster. Under high pressure, the adsorption of N2O on the sample is stronger than that of N2, and it is more affected by the composition of the mixture, which is more conducive to the separation of N2O / N2. Among them, selectivity refers to the relative separation of two gas mixtures. If one has very high adsorption performance and the other has very low adsorption performance, it is easy to separate and has good separation selectivity. The separation coefficient of the product PI-1 for the N2O / N2 binary mixed gas at a certain temperature was explored. According to Figure 6 The slopes of the three curves indicate that, for the same material and other conditions, the separation factor increases with increasing pressure. At 4 MPa, the N2O / N2 separation factor for product PI-1 is 59.60.

[0152] Analysis of the effects of PI-2, PI-6, PI-7, PI-8 and PI-9 on N2O / N2 selectivity

[0153] The N2O content is 50% binary mixed gas, and the fitted data are shown in Table 8.

[0154] Table 8. Adsorption selectivity of 298K material for N2O / N2 at 0-4 MPa pressure (YN2O=0.5)

[0155]

[0156] It can be seen that at a pressure of 4 MPa, the selectivities of PI-2, PI-6, PI-7, PI-8 and PI-9 for N2O / N2 are 10.5, 35.3, 71.9, 100.8 and 26.3, respectively.

[0157] It can be seen that the adsorbent synthesized by the present invention has a stable rigid structure, excellent thermal stability, a rich and adjustable pore structure, and can be functionalized. That is, on the one hand, it can be synthesized by selecting monomers with special groups that are basically consistent with the listed ones, so that functionalized monomers can be directly obtained or chemical modification effects can be achieved. On the other hand, the synthesized material can be blended and modified with other polymers.

[0158] When using the nitrous oxide capture and separation adsorbent of the present invention for adsorption, the specific method is as follows: accurately weigh a certain mass of the nitrous oxide capture and separation adsorbent and place it in a dry, clean stainless steel reactor, which is not limited here to any sealed container. Then, a mixed gas containing N2O, i.e., the target gas, is slowly injected into the container containing the nitrous oxide capture and separation adsorbent at a set volume or pressure to allow the gas to fully contact the adsorbent. This process is carried out in a constant temperature water bath, maintaining a constant temperature of 25°C.

[0159] When adsorbing the target gas, the gas and the adsorbent are in full contact and the process is controlled in a constant temperature environment to eliminate the interference of temperature on the adsorption process. It can also be carried out in a constant temperature box that can accurately control the temperature to keep the temperature constant. The set temperature can be determined according to actual research needs, such as 25°C or 30°C.

[0160] Then, the mixed gas was kept in contact with the adsorbent for at least 30 min to allow the adsorption to reach equilibrium, and the equilibrium was maintained for 30 min.

[0161] In the above-mentioned equilibrium process, the equilibrium time is preferably 30 minutes to 2 hours. When the time is less than 30 minutes, a complete adsorption equilibrium state cannot be achieved. When the time is longer than 2 hours, there will be little effect on the adsorption equilibrium.

[0162] A gas chromatograph is used to measure the change in gas concentration before and after adsorption. The analytical testing instrument can also use a gas sensor to measure the change in gas concentration before and after adsorption, and based on relevant calculations (such as the adsorption amount calculation formula: adsorption amount = (initial gas concentration - gas concentration after adsorption) × gas volume ÷ polyimide sample mass), the adsorption amount of the gas by the nitrous oxide capture and separation adsorbent is obtained.

[0163] It can be seen that when using the adsorbent provided by the present invention to adsorb mixed gases containing N2O, the operation is relatively simple and convenient, and operations such as continuous flow of gas can be achieved without the need for complex equipment, which is convenient for controlling experimental conditions and is very convenient when exploring the adsorption performance of different gases.

[0164] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for preparing a nitrous oxide capture and separation adsorbent, wherein: The preparation method comprises the following steps: Under a protective gas atmosphere, an acid anhydride compound, a polyamine compound, a cross-linking agent and a catalyst are added to a reaction solvent to carry out a reaction; the reaction temperature is 100-300° C., and the reaction time is 24-200 hours; After the reaction is completed, a precipitate is obtained, which is separated, washed and dried to obtain the nitrous oxide capture and separation adsorbent; The acid anhydride compound is selected from one or a combination of two or more of mellitic acid trianhydride, terphenylene [2,3-c:6,7-c':10,11-c'']trifuran-1,3,6,8,11,13-hexaketone or hexaazatrimellitic acid trianhydride; the polyamine compound is selected from one or a combination of two of tris(4-aminophenyl)amine and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine; the cross-linking agent is triaminopyrimidine; and the catalyst is isoquinoline.

2. The preparation method according to claim 1, wherein The triaminopyrimidine is selected from one or a combination of two or more of 2,4,6-triaminopyrimidine, 4,5,6-triaminopyrimidine and 2,4,5-triaminopyrimidine.

3. The preparation method according to claim 1, wherein The reaction solvent is selected from one or a combination of two or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone, 1,1,3-trimethylcyclohexenone, m-cresol, dodecane, diphenyl ether, cyclopentane, toluene, propylbenzene, mesitylene, and o-dichlorobenzene.

4. The preparation method according to claim 1, wherein The molar ratio of the total amount of the polyamine compound and the cross-linking agent to the acid anhydride is 1: (1-1.5); The molar ratio of the polyamine compound to the cross-linking agent is 1:(0.3~3); The molar ratio of the catalyst to the acid anhydride compound is (2.5-5):

1.

5. A nitrous oxide capture and separation adsorbent obtained by the preparation method according to any one of claims 1 to 4.

6. Use of the nitrous oxide capture and separation adsorbent according to claim 5 in capturing and separating N2O gas.

7. The use according to claim 6, wherein: N2O gas is captured and separated from a mixed gas containing N2O; the mixed gas containing N2O is N2O / N2, N2O / H2 or N2O / CH4.

8. The use according to claim 6, wherein: The adsorption separation temperature for capturing and separating N2O gas is 298~313K, and the adsorption separation pressure is 0~4 MPa.

9. The use according to claim 6, wherein: The nitrous oxide capture and separation adsorbent is compounded with an ionic liquid.

10. The use according to claim 9, wherein: The nitrous oxide capture and separation adsorbent is fully mixed with the ionic liquid, dried, and then ground.

11. The use according to claim 9, wherein: The ionic liquid is selected from one or a combination of two or more of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium hexafluorophosphate, and 1-(3-aminopropyl)-3-methylimidazolium bromide.

12. The use according to claim 11, wherein: The mass ratio of the nitrous oxide capture and separation adsorbent to the ionic liquid is 95:5.

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