Organometallic coordination polymers for natural gas and methane accumulation and their production methods

Abstract

This invention relates to a method for producing organometallic coordination polymers and materials obtained using the provided method. The organometallic coordination polymer synthesized according to this method has a gel structure, characterized by an effective diameter of 0.75-0.80 nm and a specific area of ​​1300-1700 m². 2 / g, micropore volume of 0.5-0.6cm³ 3 The method yields nanopores per g and improved thermal stability. The synthesis method allows for reduced material consumption during the process by using a single solvent in both the synthesis and activation stages, thus shortening the production time of the polymer gel, which is characterized by active mesopores and micropores. This makes it suitable as a matrix in various absorption processes, including natural gas storage systems.

Description

Technical Field

[0001] This invention relates to a production technology for an organometallic polymer, particularly an organometallic polymer based on the coordination of aluminum ions with 1,3,5-benzotriic acid ligands, which is synthesized by a solvothermal method and can be used for gas accumulation, especially in the storage and transportation systems of natural gas and methane. Background Technology

[0002] Organometallic polymers, also known as organometallic structures, represent a class of porous adsorbents composed of ions or metal clusters coordinated to multiple organic ligands (linkers). The wide range of organic ligands binding to different metal cations leads to a vast variation in potential porous materials with diverse porous surface properties and chemically tuned structures. These structures have been rigorously evaluated multiple times in terms of application variants, including gas storage and separation. Patents (US NO. 7202385, IPC C07C41 / 03; C07C43 / 11; C08G18 / 28; C08G65 / 26; C08G 65 / 28) disclose most of the structures described in the literature, illustrating the diversity of existing organometallic polymers.

[0003] Organometallic polymers possess unique structural and energy characteristics, including regular crystal structures and high specific surface areas (up to 10,000 m²). 2 With high micropore volume, which typically exceeds similar characteristics of zeolites and activated carbon, they are used as highly efficient adsorbents, for example, for gas storage and separation [TAMakal, JRLi, W.Lu, HCZhou Methane storage in advanced porous materials / / Chem.Soc.Rev.2012.V.41.P.7761-7779].

[0004] The production of high-performance organometallic polymers for use in gas storage and transportation systems requires them to have not only appropriate adsorption properties but also thermal stability.

[0005] The most well-known and widely used organometallic polymers have the potential to store and separate gases, including methane [A.Yu.Tsyvadze, O.Ye.Aksyutin, AGIshkov, AAFomkin, I.Ye.Menshchikov, A.A.Pribylov, V.V.sayeva, L.M.Kustov, A.V.Shkolin, Ye.M.Strizhenov. Adsorption of methane on the organometallic framework structure MOF-199 under high pressures within the range of supercritical temperatures, Physicochemistry of surface and material protection. 2016. Vol.52 No.1. P.24-29]. [Baichuan Sun, Sibnath Kayal, Anutosh Chakraborty, Study of HKUST(Copperbenzene-1,3,5-tricarboxylate, Cu-BTCMOF)-1 metalorganic frameworks for CH4 adsorption: An experimental investigation with GCMC (grandcanonical Monte-carlo) simulation], Energy (2014), 1-9] is related to the HKUST-1 family of MOF-199, as disclosed in, for example, patents (US 9925516, IPCB01D53 / 02; B01J20 / 22; B01J20 / 28). However, MOF-199 suffers from insufficient thermal stability due to the strength of the metal-ligand bond, as it utilizes the divalent copper cation Cu(II). This problem can be addressed by replacing the divalent copper cation with another cation having a higher valence.

[0006] For this problem, the preferred choice is to use trivalent aluminum cation Al(III) because aluminum-based organometallic polymers have high thermal stability and mechanical strength, developed micropore volumes for gaseous accumulation, and relatively low production costs, for example, compared to organometallic polymers based on zirconium (Zr(IV)) or titanium (Ti(IV)) with similar mechanical properties.

[0007] Among the methods for synthesizing organometallic polymers, there are generally two well-known improvements to the methods: solvothermal methods, such as [RU 2457213 C1, IPC C07F 11 / 00, published on July 27, 2012] and methods using UHF, such as patents [RU2578599C1, IPC CO8F 293 / 00, B01J 32 / 00].

[0008] The solvothermal method described in part in Russian Federation Patent RU 2457213 involves mixing an alkaline component, specifically chromium(III) nitrate and terephthalic acid, in an aqueous solution while heating. The mixture is heated to 220°C in a sealed container at a rate of 11.5°C / min and then maintained thereafter.

[0009] A method for producing coordination polymers under UHF, for example in RU 2578599, comprises mixing an aluminum salt of an AlCl3×6H2O compound with an organic 2-amino-1,4-benzenedicarboxylic acid, and adding a mixture of water and a polar organic solvent, respectively, at a weight ratio of 1:1 / 5. The resulting reaction mixture is then heated under 200 W UHF radiation at atmospheric pressure and a temperature of 120-130°C. A solvent with a boiling point exceeding 130°C is used as the polar organic solvent, which can be effectively heated under UHF radiation, such as dimethyl sulfoxide, N,N'-dimethylformamide, or N,N'-diethylformamide.

[0010] The disadvantage of these methods is that they allow for the production of unactivated organometallic polymers, which require labor-intensive selection of activation conditions to remove solvent residues while maintaining the material structure used as a gas absorbent.

[0011] The closest analogue and the result obtained is a method [US 9878906 B2, IPC C01B 3 / 00, B01D 53 / 02, published January 30, 2018], which involves the interaction of at least one metal compound with at least one bidentate organic compound in a mixing process at a pressure not exceeding 2 bar (absolute pressure), wherein the at least one metal compound and at least one bidentate organic compound can coordinate with the metal in the presence of a non-aqueous organic solvent selected from DMF, DEF, and NMP to produce a porous organometallic structure, wherein the metal is represented by Mg, Ca, be, Sr, Ga, or Al; and an organic compound having at least two atoms selected from oxygen, sulfur, or nitrogen can coordinate with the metal through these atoms, wherein at least one bidentate organic compound is represented by a dicarboxylic acid, tricarboxylic acid, or tetracarboxylic acid. The reaction should be carried out without additional base, and the formed organometallic framework should be additionally calcined at a temperature not exceeding 250°C. Example 13 of this invention is closest to the result obtained. The synthesis of the framework organometallic polymer using N,N'-dimethylformamide solvent was carried out as follows: 7.8 g of 1,3,5-benzenetricarboxylic acid (BTC) and 22.9 g of Al(NO3)3*9H2O were dissolved in 520.5 g of N,N'-dimethylacetamide at 130 °C for 4 days, while stirring the resulting suspension. The resulting suspension was washed twice with 100 ml of N,N'-dimethylacetamide and then four times with 100 ml of methanol. The filter containing the precipitated material was then dried at 200 °C for 16 hours using a thermal vacuum drying method. The obtained organometallic framework powder was annealed at 330 °C for activation in a muffle furnace and purged with air at a rate of 100 L / h for 3 days. Therefore, the furnace heating rate was 75 °C / h. The obtained aluminum-based framework organometallic polymer had a thickness of 1791 m... 2 The specific surface area per g was determined according to the Langmuir method. Summary of the Invention

[0012] The purpose of this invention is to develop a method for synthesizing an organometallic coordination polymer having an organometallic gel structure based on aluminum ions coordinated with 1,3,5-benztriac ligands. This polymer has a good nanoporous surface and improved thermal stability, allowing the obtained organometallic gel to be used as an adsorbent in gas, particularly natural gas and methane, transport and storage systems.

[0013] The technical result that this invention aims to achieve is:

[0014] - Production and maintenance of the gel structure of the organometallic coordination polymer to be synthesized;

[0015] - Improve its thermal stability;

[0016] -Reduce material and energy costs in production by reducing synthesis time and using a single solvent in the synthesis and washing stages.

[0017] This technical result is achieved through the following fact: in a method for producing organometallic coordination polymers for accumulating natural gas and methane, the method includes a synthesis stage comprising: the interaction of an equimolar amount of aluminum nitrate crystalline hydrate and 1,3,5-benzoic acid dissolved in an equimolar amount or excess of an aprotic polar organic solvent with a boiling point exceeding 80°C; however, the aluminum nitrate crystalline hydrate solution is heated to 110°C, and the 1,3,5-benzoic acid solution is heated to 80-110°C; under vigorous stirring, the heated 1,3,5-benzoic acid solution is added dropwise to the heated aluminum nitrate solution at a rate of 5-15 vol.% per minute, and the solution mixture is added at a rate of 10-15°C per hour. The mixture is heated to 140°C and held until a sol is formed. The sol is then placed in an autoclave and held at 100-150°C for 2-3 days until an organometallic coordination polymer with a gel structure is obtained. The activation stage includes washing the synthesized organometallic coordination polymer with a gel structure with the aprotic polar organic solvent used in the synthesis stage, heating it to 40-60°C using a vacuum filtration system with a pressure drop of at least 90 kPa, drying it at room temperature, drying it in a drying oven at 100-150°C, and treating it in a hot vacuum chamber at a temperature of 120-300°C and a residual pressure of 0.26 kPa. The activation stage terminates after the organometallic coordination polymer with a gel structure has reached weight stability.

[0018] Organometallic coordination polymers with a gel structure for accumulating natural gas and methane are thermally stable at temperatures of at least 500°C and have an effective inner diameter of 0.75-0.80 nm and a specific area of ​​1300-1700 m². 2 / g, micropore volume is 0.5-0.6cm 3 / g, total micropore volume is 1.0-1.8cm³ 3 / g of holes. Attached Figure Description

[0019] The present invention group is described in the table and the accompanying drawings:

[0020] Table 1—Chemical composition of the synthesized organometallic gel, where: Wt—weight percentage, At—atomic percentage;

[0021] Table 2—Porous structure parameters of the synthesized organometallic gel samples, where: V0—specific micropore volume, cm³ 3 / g; E0—Nitrogen adsorption characteristic energy, kJ / mol; D—Effective inner diameter of micropores, nm; E—Benzene adsorption characteristic energy, kJ / mol; S BET —Based on the specific surface area according to the BET method, m2 / g;V s —Total pore volume, cm³ 3 / g;S me —Area of ​​the central hole, m² 2 / g;V me —Volume of the mesopore, cm³ 3 / g.

[0022] Figure 1 —A scanning electron microscope image of an organometallic coordination polymer sample with a gel structure;

[0023] Figure 2 —Infrared spectrum of synthesized organometallic coordination polymers with gel structure—solid line; aluminum-based organometallic polymer (prototype)—dashed line.

[0024] Figure 3 —Diffraction pattern of the synthesized organometallic coordination polymer with gel structure—top line; aluminum-based organometallic polymer (prototype)—bottom line.

[0025] Figure 4 —Heatmap: Solid line—Sample of synthesized organometallic coordination polymer with gel structure; Dashed line—Organometallic polymer (prototype) with aluminum-based gel structure.

[0026] Figure 5 —Isothermal curves of nitrogen adsorption / desorption of sample (1) at 77 K. Bright label —Adsorption. Dark label —Desorption.

[0027] Figure 6 —A skeletal model of synthesized organometallic coordination polymer fragments, where D is the effective inner diameter of the micropores. Detailed Implementation

[0028] The proposed invention group is implemented as follows.

[0029] Example 1

[0030] 1,3,5-Benzotriic acid (1,3,5-Benzotricarboxylic acid (H3BTC)) and aluminum nitrate hydrate Al(NO3)3·9H2O were dissolved in the organic solvent N,N'-dimethylformamide at a molar ratio of 1:1 (1 mole of solvent = 1 mole of acid, 1 mole of solution = 1 mole of salt). The resulting solution was heated (aluminum salt solution to 110°C, 1,3,5-Benzotriic acid solution to 80°C). Then, the heated 1,3,5-Benzotriic acid solution was added dropwise to the aluminum salt solution at a rate of 5-15 vol.% / min, and the mixture was vigorously stirred with a magnetic stir bar. The temperature of the reaction mixture was gradually increased to 140°C and maintained until a sol was formed (the solution thickened). The obtained sol was placed in an autoclave with a tightly threaded cap and a fluoroplastic liner, and then placed in a furnace for synthesis at 100°C, gradually heated to 140°C, and maintained for two days. Activation was performed as follows: the resulting organometallic gel (OMG) residue was separated from the mother liquor by thermal vacuum filtration (desorption of solvent molecules), particularly by repeated washing under vacuum conditions with a solvent (150 ml N,N'-dimethylformamide heated to 60 °C) at a pressure drop of at least 90 kPa. The residue was then dried first under standard conditions, followed by drying in a drying oven at 100 °C, with the temperature increased to 140 °C over 20 hours, and then maintained at 140 °C for another 4 hours. Under these drying conditions, surface moisture was first removed (at 100 °C), followed by removal of interstitial unbound moisture (100–140 °C) to stabilize the synthesized OMG framework. The obtained OMG sample was activated in a thermal vacuum chamber at 200 °C and a residual pressure of 0.26 kPa (2 mm Hg) to maximize the removal of interstitial bound (crystalline hydrate) moisture and solvent until a constant weight was obtained (approximately 6 hours).

[0031] The obtained sample is an organometallic coordination polymer (OMCP) based on aluminum ions coordinated to a 1,3,5-benzenetricarboxylic acid ligand, possessing the gel structure and surface chemical composition specified in Table 1. Its physical and chemical properties are confirmed by the analytical results shown in the figure below: Figure 2 -Infrared spectral absorption characteristics of the material; Figure 3 —Diffraction pattern; Figure 4 —Temperature spectrum; Figure 5 —Adsorption isotherm curves. Scanning electron microscope images of the obtained OMCP samples with gel structures ( Figure 1 The results showed crystals of varying sizes and small amounts of amorphous phase between them, indicating a less uniform molar mass distribution in the obtained polymer compared to the prototype due to the shortened synthesis time. Selecting specific activation conditions to maximize the removal of free and bound liquid phases helps maintain the porous structure and provides acceptable strength and thermal stability for OMCP. Figure 4This characteristic is preferred when natural gas accumulators are subjected to high aerodynamic loads during operation, which explains the advantages of the polymer gel structure obtained for the specific intended use compared to the highly crystalline OMCP structure (which is solid but brittle).

[0032] The infrared absorption bands of the synthesized OMCP Figure 2 , in the range of 663-766cm -1 Bond vibrations corresponding to those within the benzene nucleus and outside the aromatic ring plane were observed within the range of 827-1153 cm⁻¹. -1 The bands that appear between these bands are related to symmetric and asymmetric deformation vibrations OC=O. These bands are observed at 1368, 1445, and 1640 cm⁻¹. -1 The strong absorption peaks at these locations are related to the CO bond in the COOH group (in 1,3,5-benzotriacrylic acid), as well as the deformation vibrations of the asymmetric and symmetric C=O groups. These characteristics also indicate that OMCP has achieved the required chemical composition.

[0033] Figure 4 The results of thermal stability measurements of the synthesized OMCP with a gel structure shown indicate that its thermal decomposition occurs at temperatures exceeding 500°C. This is evidence of improved thermal stability compared to known organometallic coordination polymers based on aluminum cations coordinated to 1,3,5-benzotriic acid ligands.

[0034] Using the BET method and the micropore volume filling theory, based on the isotherm curve of standard nitrogen vapor at -196.15℃ (77K), such as Figure 5 As shown, the parameters of the porous structure of the organometallic gel of the synthesized sample (1) (see Table 2) were analyzed. The adsorption isotherm form is characteristic of microporous adsorbents. Figure 6 Figures 7 and 8 illustrate a framework model of organometallic gel (OMG) fragments, schematically showing their geometry and porous properties.

[0035] Example 2

[0036] The difference from Example 1 is that the 1,3,5-benzoic acid solution was heated to 110°C and then added to the aluminum nitrate hydrate solution at a rate of 1 ml / min while stirring. The temperature of the synthesis stage was increased from 100°C to 120°C and then maintained at 120°C for 60 hours. The drying stage in the drying oven was carried out at 100°C and gradually heated to 120°C. It was maintained in a thermal vacuum chamber at 120°C. The results of the porous structure determination of the obtained organometallic gel (2) samples are given in Table 2.

[0037] Example 3

[0038] The difference from Example 1 is that 1,3,5-benzenetricaric acid and aluminum nitrate hydrate were dissolved in the organic solvent diethyl sulfoxide at a molar ratio of 1:2 (1 mole of acid for every 2 moles of solvent, 1 mole of salt for every 2 moles of solvent). The synthesis stage was carried out at a temperature increased from 100°C to 150°C, and then maintained at 150°C for 48 hours. The drying stage in the drying oven was carried out at a temperature of 100°C, gradually heated to 130°C. It was then maintained in a thermal vacuum chamber at 250°C. The results of the porous structure determination of the obtained organometallic gel (3) samples are given in Table 2.

[0039] Example 4

[0040] The difference from Example 1 is that diethylformamide was used as the solvent, and the synthesis stage was carried out at 120°C for 60 hours. The drying stage in the drying oven was carried out at 100°C, gradually heated to 120°C. It was then maintained in a thermal vacuum chamber at 300°C. Table 2 shows the results of the porous structure determination of the obtained organometallic gel (4) sample.

[0041] Example 5

[0042] The difference between this and Example 1 is that the synthesis stage was carried out at 130°C, the temperature was raised to 140°C, and then maintained at 140°C for 48 hours; the activation stage was carried out by filtration with dimethyl sulfoxide as solvent, heating to 40°C, drying in a drying oven at 100°C, heating to 140°C, and maintaining it in a thermal vacuum chamber at 160°C. Table 2 shows the results of the porous structure determination of the obtained organometallic gel (5) sample.

[0043] The provided invention group allows for the preparation of organometallic coordination polymers with gel structures, which have a good internal surface consisting of micropores and mesopores, and higher thermal stability compared to similar materials. Their drying and activation parameters help to maximize the retention of the porous properties obtained during the synthesis stage, which is often evidence of achieving the desired technical results.

[0044] Table 1

[0045] element Wt% At% Carbon — C 46.16 55.37 Oxygen—O 43.35 39.03 Aluminum — Al 10.49 5.60

[0046] Table 2

[0047]

Claims

1. A method for producing an organometallic coordination polymer that accumulates natural gas, methane, characterized by, The method comprises a synthesis phase and an activation phase, the synthesis phase comprising: interaction of equimolar quantities of aluminum nitrate crystalline hydrate and 1,3,5-benzene tricarboxylic acid dissolved in equimolar quantities or excess of an aprotic polar organic solvent with a boiling point exceeding 80°C in relation to the reagents; wherein the aluminum nitrate crystalline hydrate solution is heated to 110°C, the 1,3,5-benzene tricarboxylic acid solution is heated to 80-110°C, then the heated 1,3,5-benzene tricarboxylic acid solution is added dropwise to the heated aluminum nitrate crystalline hydrate solution at a rate of 5-15 vol.% per minute under vigorous stirring, the solution mixture is heated to 140°C until a sol is formed, then the sol is polymerized at 100-150°C for 2-3 days until an organometallic coordination polymer with a gel structure is obtained; the activation phase comprising: washing the synthesized organometallic coordination polymer with a gel structure with the non-protic polar organic solvent used in the synthesis phase and heated to 40-60°C in a vacuum with a pressure drop of at least 90 kPa, drying first under standard conditions for 24 hours and then at 100°C-140°C for 24 hours, in particular: first drying under standard conditions, then drying in an oven at 100°C, increasing the temperature to 120-140°C over a period of 20 hours, then maintaining at 120-140°C for a further 4 hours, then heat vacuum treatment at a temperature of 120-300°C and a residual pressure of 0.26 kPa for up to 6 hours; the activation phase being terminated after the weight of the organometallic coordination polymer with a gel structure is stabilized.

2. An organometallic coordination polymer having a gel structure for accumulating natural gas, methane, prepared using the method of claim 1, characterized by, The organometallic coordination polymer is thermally stable at temperatures of at least 500°C, has an effective internal diameter of 0.75-0.80 nm, a specific surface area of 1300-1700 m 2 / g, a micropore volume of 0.5-0.6 cm 3 / g, a total micropore volume of 1.0-1.8 cm 3 / g of pores.

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