Chlorine-modified metal-organic framework materials, preparation and use thereof

Abstract

The present application relates to the field of gas adsorption separation, and more particularly to a chlorine-modified metal organic framework material and preparation and application thereof, the present application dissolves cobalt nitrate hexahydrate, alpha, beta-di(4-pyridyl)glycol and 5-chloro isophthalic acid in a solvent, then transfers the mixture to a reaction kettle, and reacts at 60-80 DEG C for 12-48h; pink powder is obtained by filtration, and is washed; finally, the solvent in the crystal pore is removed by activation in vacuum at 150-200 DEG C for 6-12h to obtain the chlorine-modified metal organic framework material. The present application provides a suitable pore size and pore chemical environment for gas molecule adsorption separation, and provides a new idea for CH4 / N2 separation, and is expected to replace the current high-energy consumption methane enrichment mode, and has great application potential in the industrial application of adsorption separation of low-concentration coal bed methane.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of gas adsorption separation, in particular to a chlorine-modified metal-organic framework material and its preparation and application. BACKGROUND

[0002] Natural gas, mainly methane (CH4), is considered as a clean and efficient energy. Under the driving of the increasing pursuit of clean energy, the share of coalbed methane in primary energy consumption has reached 23.5%. Coalbed methane, as a typical unconventional natural gas, is an important supplement of natural gas. However, a large amount of coalbed methane mined from the underground is introduced with air, which reduces the concentration of CH4. This low-concentration coalbed methane (CH4 content < 30%) cannot be used as fuel and is usually released into the atmosphere, which has a great impact on the greenhouse effect. Since the main impurity in low-concentration coalbed methane is nitrogen (N2), the separation of CH4 from N2 to produce high-purity CH4 with high added value has important industrial significance. The mature separation process currently available for CH4 purification is cryogenic distillation, which has high energy consumption. Adsorption separation based on physical adsorbents has become an effective alternative to cryogenic distillation. However, due to the very similar physicochemical properties of CH4 and N2, their effective separation is still a formidable challenge. SUMMARY

[0003] The present application provides a chlorine-modified metal-organic framework material and its preparation and application to solve the problem that CH4 is difficult to be effectively separated due to its very similar physicochemical properties to N2.

[0004] The present application is realized by the following technical scheme: a chlorine-modified metal-organic framework material, the chemical formula of which is: 20 H 16 ClCoN2O 6.5 ; the crystallographic data are as follows: belonging to the orthorhombic system, space group Cmcm, unit cell parameters: α = 90°, β = 90°, γ = 90°, Z = 4, F (000) = 984.0.

[0005] In a second aspect, the present application provides a preparation method of the chlorine-modified metal-organic framework material, comprising the following steps:

[0006] Dissolve cobalt nitrate hexahydrate, α, β-bis (4-pyridyl) ethylene glycol and 5-chloroisophthalic acid in a solvent, then transfer the mixture to a reaction kettle, and react at 60-80°C for 12-48h; obtain pink powder by filtration, and wash; finally, activate at 150-200°C in vacuum for 6-12h to remove the solvent in the crystal pores, to obtain the chlorine-modified metal-organic framework material.

[0007] As a further improvement of the technical scheme of the preparation method of the application, the molar ratio of the cobalt nitrate hexahydrate, alpha, beta-di(4-pyridyl)glycol and 5-chloroisophthalic acid is 1:0.5-1.5:0.50-1.5.

[0008] As a further improvement of the technical scheme of the preparation method of the application, the molar ratio of the cobalt nitrate hexahydrate, alpha, beta-di(4-pyridyl)glycol and 5-chloroisophthalic acid is 1:1:1.

[0009] As a further improvement of the technical scheme of the preparation method of the application, the solvent is a mixed solvent of DMF and methanol.

[0010] As a further improvement of the technical scheme of the preparation method of the application, the volume ratio of DMF and methanol in the mixed solvent is 0.8-1.2:1.

[0011] In a third aspect, the application provides an application of the chlorine-modified metal-organic framework material in methane / nitrogen adsorption separation.

[0012] The application further provides an application of the chlorine-modified metal-organic framework material prepared by the preparation method of the chlorine-modified metal-organic framework material in methane / nitrogen adsorption separation.

[0013] As a further improvement of the technical scheme of the application, the chlorine-modified metal-organic framework material preferentially adsorbs methane in a methane / nitrogen mixer.

[0014] The chlorine-modified metal-organic framework material and the preparation and application thereof provided by the application have the following advantages compared with the prior art.

[0015] The application effectively improves the selectivity of CH4 / N2 by introducing a functional group-Cl on the ligand, realizes effective CH4 / N2 separation, and provides a suitable pore size and pore channel chemical environment for gas molecule adsorption separation, and provides a new idea for CH4 / N2 separation, which is expected to replace the current high-energy consumption methane enrichment mode and has great application potential in the industrial application of low-concentration coal bed methane adsorption separation. BRIEF DESCRIPTION OF DRAWINGS

[0016] The accompanying drawings, which are incorporated into and form a part of the specification, illustrate embodiments consistent with the application and, together with the description, serve to explain the principles of the application.

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments or prior art description. Obviously, for those skilled in the art, other drawings can also be obtained based on these drawings without creative effort.

[0018] Figure 1 Structure diagram of the material obtained in Example 1.

[0019] Figure 2 X-ray diffraction pattern of the material obtained in Example 1, which is obtained by Figure 2 It can be seen that the powder X-ray diffraction of the synthesized sample is highly consistent with the simulation diagram, proving that the synthesized sample has high purity.

[0020] Figure 3 77K N2 adsorption-desorption isotherm and pore size distribution diagram of the material obtained in Example 1(a) and Comparative Example (b). It can be seen from the diagram that the pore sizes of the comparative sample and the compound are both 0.62 nm.

[0021] Figure 4 Adsorption isotherm of Example 1 and the comparative sample on methane and nitrogen at normal temperature and pressure. It can be seen from the diagram that the compound shows methane > nitrogen adsorption capacity, proving that the material has preferential adsorption on methane.

[0022] Figure 5 Methane and nitrogen adsorption heat of Example 1 and the comparative sample. It can be seen from the diagram that the methane adsorption heat of the compound of Example 1 is higher than that of the comparative sample, indicating that the introduction of the functional group -Cl improves the force on methane.

[0023] Figure 6 Selectivity diagram of Example 1 and the comparative sample on methane / nitrogen. It can be seen from the diagram that the selectivity of the compound of Example 1 at 1 bar reaches 9, which is higher than 5.3 of the comparative sample, proving that the introduction of the functional group -Cl has more excellent selectivity on methane / nitrogen.

[0024] Figure 7 Dynamic breakthrough curve of Example 1(b) and Comparative Example (a). It can be seen from the diagram that nitrogen is penetrated out before methane, proving that the compound of Example 1 has better separation performance than the comparative sample. DETAILED DESCRIPTION

[0025] In order to more clearly understand the above-mentioned purposes, features and advantages of the present application, the solutions of the present application will be further described below. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0026] Many specific details are set forth in the following description in order to provide a thorough understanding of the application. However, the application can be practiced according to the claims without some or all of these details. In other instances, well known process steps have not been described in detail in order not to unnecessarily obscure the application.

[0027] The application provides a specific embodiment of a chlorine-modified metal organic framework material, with a chemical formula of C 20 H 16 ClCoN2O 6.5 ; crystallographic data: belonging to the orthorhombic system, space group Cmcm, cell parameters: α = 90°, β = 90°, γ = 90°, Z = 4, F(000) = 984.0.

[0028] The application further provides a preparation method of the chlorine-modified metal organic framework material, comprising the following steps:

[0029] Dissolve cobalt nitrate hexahydrate, α, β-bis(4-pyridyl)glycol and 5-chloroisophthalic acid in a solvent, then transfer the mixture into a reaction kettle, and react at 60-80°C for 12-48h; obtain pink powder by filtration, and wash; finally, activate at 150-200°C in vacuum for 6-12h to remove the solvent in the crystal channel, to obtain the chlorine-modified metal organic framework material.

[0030] The application is a chlorine-modified metal organic framework material generated by using cobalt nitrate hexahydrate as a metal source, and using α, β-bis(4-pyridyl)glycol and 5-chloroisophthalic acid as organic ligands, and reacting in a solvothermal environment. In the application, the solvothermal reaction is carried out in an oven, and of course, the reaction container of the solvothermal reaction of the application is not limited to the oven.

[0031] In an embodiment provided by the application, the molar ratio of the cobalt nitrate hexahydrate, α, β-bis(4-pyridyl)glycol and 5-chloroisophthalic acid is 1:0.5-1.5:0.50-1.5. Preferably, the molar ratio of the cobalt nitrate hexahydrate, α, β-bis(4-pyridyl)glycol and 5-chloroisophthalic acid is 1:1:1.

[0032] In an embodiment provided by the application, the solvent is a mixed solvent of DMF and methanol. Preferably, the volume ratio of DMF to methanol in the mixed solvent is 0.8-1.2:1. Further preferably, the ratio is 1:1.

[0033] The application further provides an application of the chlorine-modified metal organic framework material in methane / nitrogen adsorption separation.

[0034] Specifically, the chlorine-modified metal-organic framework material preferentially adsorbs methane in a methane / nitrogen mixer.

[0035] The specific embodiments of the present application are described in detail below.

[0036] Example 1:

[0037] Co(NO3)3·6H2O (0.75 mmol), α,β-bis(4-pyridyl)ethyleneglycol (0.75 mmol) and 5-chloroisophthalic acid (0.75 mmol) were dissolved in a mixed solution of DMF / MeOH (1 / 1, 60 mL), and then the mixture was transferred to a Teflon-lined stainless steel autoclave and placed in a 70°C oven for 24 h. After the reaction was completed, the mixture was cooled to room temperature, and the compound was obtained by filtration, and then washed with fresh DMF and MeOH three times, respectively. The obtained crystal powder was dried at 180°C under vacuum for 8 hours to obtain the chlorine-modified metal-organic framework material.

[0038] Table 1 is the crystallographic parameters of the compound prepared in Example 1

[0039] Table 1 Crystal data

[0040]

[0041]

[0042] Example 2:

[0043] Co(NO3)3·6H2O (0.75 mmol), α,β-bis(4-pyridyl)ethyleneglycol (0.75 mmol) and 5-chloroisophthalic acid (0.75 mmol) were dissolved in a mixed solution of DMF / MeOH (0.8 / 1, 60 mL), and then the mixture was transferred to a Teflon-lined stainless steel autoclave and placed in a 70°C oven for 24 h. After the reaction was completed, the mixture was cooled to room temperature, and the compound was obtained by filtration, and then washed with fresh DMF and MeOH three times, respectively. The obtained crystal powder was dried at 180°C under vacuum for 8 hours to obtain the chlorine-modified metal-organic framework material.

[0044] Example 3:

[0045] Co(N03)3-6H20 (0.75 mmol), a, b-bis(4-pyridyl)ethyleneglycol (0.75 mmol) and 5-chloroisophthalic acid (0.75 mmol) were dissolved in a mixed solution of DMF / MeOH (1 / 1, 60 mL), and then the mixture was transferred into a Teflon-lined stainless steel reaction vessel, which was placed in an 80 °C oven for 24 h. After the reaction was completed, the mixture was allowed to cool to room temperature, and the compound was obtained by filtration, followed by washing with fresh DMF and MeOH three times, respectively. The obtained crystal powder was dried at 180 °C under vacuum for 8 h to obtain the chloro-modified metal-organic framework material.

[0046] Comparative Example (Preparation of Comparative Example)

[0047] Co(N03)3-6H20 (0.75 mmol), a, b-bis(4-pyridyl)ethyleneglycol (0.75 mmol) and isophthalic acid (0.75 mmol) were dissolved in a mixed solution of DMF / MeOH (1 / 1, 60 mL), and then the mixture was transferred into a Teflon-lined stainless steel reaction vessel, which was placed in a 70 °C oven for 24 h. After the reaction was completed, the mixture was allowed to cool to room temperature, and the compound was obtained by filtration, followed by washing with fresh DMF and MeOH three times, respectively. The obtained crystal powder was dried at 180 °C under vacuum for 8 h to obtain the metal-organic framework material.

[0048] Test Example 1

[0049] Single gas adsorption test

[0050] About 130 mg of the comparative example and the compound (crystal powder obtained in Example 1) were prepared, respectively, and both were vacuum degassed at 453 K under high vacuum for 3-5 h, and N2adsorption isotherms at 77 K were obtained using a Micromeritics ASAP 2460 instrument (N2purity used was 99.999%). The pore size of both the comparative example and the compound was analyzed using a DFT model, and the pore size of both was 0.62 nm, as shown in Figure 3 .

[0051] About 130 mg of the comparative example and the compound (crystal powder obtained in Example 1) were prepared, respectively, and both were vacuum degassed at 453 K under high vacuum for 5 h, and CH4and N2adsorption isotherms at 298 K, 273 K were obtained using a Micromeritics ASAP 2460 instrument. The purity of CH4and N2used was 99.999%, and the obtained adsorption data are shown in Figure 4 .

[0052] Test Example 2

[0053] Adsorption heat test:

[0054] Using the single gas adsorption isotherms measured in Experimental Example 1 at 273 and 298 K and the Clausius-Clapeyron equation:

[0055]

[0056] The adsorption heats of the comparative sample and the compound were calculated, as shown in Table 2. Figure 5

[0057] Here, Qst is the adsorption heat (kJ / mol), R is the universal gas constant, T represents the temperature, p represents the pressure (kPa), and q represents the adsorption capacity (mmol / g).

[0058] Selectivity test:

[0059] To evaluate the gas separation ability of the sample, IAST calculation was performed for CH4 / N2(50:50, v / v) adsorption based on the single gas adsorption isotherms obtained in Experimental Example 1. The selectivity of the comparative sample was 5.34, and the selectivity of the compound was 9, with an increase of 3.6 in selectivity, as shown in Table 3. Figure 6

[0060] Dynamic breakthrough test:

[0061] Dynamic breakthrough tests were performed on both the comparative sample and the compound. 0.6 g of the comparative sample and the compound powder were respectively placed in a stainless steel column, and then activated at 453 K for 5 hours. At the same time, the adsorption bed was purged with helium (He, ≥99.999%) at a rate of 15 mL / min. After the bed temperature was lowered to 298 K, the mixed gas CH4 / N2(50:50, v / v) (flow rate: 10 mL / min) was introduced, and the outlet gas was analyzed by mass spectrometry. Using the data detected by mass spectrometry, the breakthrough curves were plotted as shown in Figure 2, and it was found that the compound of Example 1 had better separation performance than the comparative sample. Figure 7

[0062] The above description is merely a specific implementation of the present application, enabling those skilled in the art to understand or implement the present application. Although detailed descriptions are made with reference to the foregoing embodiments, those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent replacements can be made to some or all of the technical features; and such modifications or replacements do not cause the essence of the corresponding technical solution to deviate from the scope of the technical solutions of the embodiments, and should be covered in the protection scope of the claims.​​​

Claims

1. Use of a chlorine-modified metal-organic framework material in methane / nitrogen adsorptive separation, characterized in that, The chemical formula of the chlorine-modified metal-organic framework material is: C 20 H 16 ClCoN2O 6.5 ; crystallographic data: belongs to the orthorhombic system, space group Cmcm, cell parameters: a = 13.7022(8) Å, b = 7.6327(4) Å, c = 22.1516(12) Å, α = 90°, β = 90°, γ = 90°, V = 2316.7(2) Å3, Z = 4, F(000) = 984.

0.

2. A method for preparing a chlorine-modified metal-organic framework material, the use of the chlorine-modified metal-organic framework material obtained in the adsorptive separation of methane / nitrogen, characterized in that The preparation method of the chlorine-modified metal organic framework material comprises the following steps: Dissolve cobalt nitrate hexahydrate, α, β-di(4-pyridyl)glycol and 5-chloroisophthalic acid in a solvent, then transfer the mixture into a reaction kettle, and react at 60-80 ℃ for 12-48 h; obtain pink powder by filtration, and wash; finally, activate in vacuum at 150-200 ℃ for 6-12 h to remove the solvent in the crystal pores, to obtain the chlorine-modified metal organic framework material.

3. The use according to claim 2, wherein The molar ratio of the cobalt nitrate hexahydrate, α, β-di(4-pyridyl)glycol and 5-chloroisophthalic acid is 1:0.5-1.5:0.50-1.

5.

4. The use according to claim 3, wherein the compound is ###0002### The molar ratio of the cobalt nitrate hexahydrate, α, β-di(4-pyridyl)glycol and 5-chloroisophthalic acid is 1:1:

1.

5. The use according to claim 2, wherein the compound is ###0002### The solvent is a mixed solvent of DMF and methanol.

6. The use according to claim 5, wherein the compound is ###0002### The volume ratio of DMF to methanol in the mixed solvent is 0.8-1.2:

1.

7. The use according to claim 2, wherein the compound is ###00003### or a pharmaceutically acceptable salt thereof. The chlorine-modified metal organic framework material preferentially adsorbs methane in a methane / nitrogen mixer.

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