Chlorine modified metal organic framework material as well as preparation and application thereof

Abstract

The invention relates to the field of gas adsorption separation, in particular to a chlorine-modified metal organic framework material and preparation and application thereof.The chlorine-modified metal organic framework material is prepared by the steps that cobalt nitrate hexahydrate, alpha, beta-bis (4-pyridyl) ethylene glycol and 5-chloroisophthalic acid are dissolved in a solvent, then the mixture is transferred into a reaction kettle, and a reaction is conducted for 12-48 h at the temperature of 60-80 DEG C; filtering to obtain pink powder, and washing; and finally, activating in vacuum at 150-200 DEG C for 6-12 hours to remove the solvent in crystal pore channels, thereby obtaining the chlorine-modified metal organic framework material. According to the method, a proper pore diameter and pore channel chemical environment is provided for gas molecule adsorption separation, a new thought is provided for CH4 / N2 separation, the method is expected to replace an existing high-energy-consumption methane enrichment mode, and the method has great application potential in industrial application of adsorption separation of low-concentration coal bed gas.

Description

Technical Field

[0001] The invention relates to the field of gas adsorption separation, and in particular to a chlorine-modified metal organic framework material and the preparation and application thereof. Background Art

[0002] Natural gas, mainly methane (CH4), is considered a clean and efficient energy source. Driven by the growing 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 to natural gas. However, a large amount of coalbed methane mined from 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 coal seams is nitrogen (N2), separating CH4 from N2 to produce high-value-added high-purity CH4 is of great 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, since the physicochemical properties of CH4 are very similar to those of N2, their effective separation remains a daunting challenge. Summary of the invention

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

[0004] The present invention is realized by the following technical scheme: a chlorine-modified metal organic framework material, the chemical formula of which is: C 20 H 16 ClCoN2O 6.5 ; Crystallographic data: belongs to 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 invention provides a method for preparing a chlorine-modified metal organic framework material, comprising the following steps:

[0006] Cobalt nitrate hexahydrate, α, β-di(4-pyridyl)ethylene glycol and 5-chloroisophthalic acid are dissolved in a solvent, and then the mixture is transferred to a reactor and reacted at 60-80°C for 12-48 hours; a pink powder is obtained by filtration and washed; finally, the powder is activated in a vacuum at 150-200°C for 6-12 hours to remove the solvent in the crystal pores to obtain a chlorine-modified metal organic framework material.

[0007] As a further improvement of the technical solution of the preparation method of the present invention, the molar ratio of the cobalt nitrate hexahydrate, α, β-di(4-pyridyl)ethylene glycol and 5-chloroisophthalic acid is 1:0.5-1.5:0.50-1.5.

[0008] As a further improvement of the technical solution of the preparation method of the present invention, the molar ratio of the cobalt nitrate hexahydrate, α, β-di(4-pyridyl)ethylene glycol and 5-chloroisophthalic acid is 1:1:1.

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

[0010] As a further improvement of the technical solution of the preparation method of the present invention, the volume ratio of DMF to methanol in the mixed solvent is 0.8-1.2:1.

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

[0012] The present invention further provides a method for preparing a chlorine-modified metal organic framework material and application of the prepared chlorine-modified metal organic framework material in methane / nitrogen adsorption separation.

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

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

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

[0016] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 This is a schematic diagram of the structure of the material obtained in Example 1.

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

[0020] Figure 3 The N2 adsorption-desorption isotherms and pore size distribution diagrams of the materials obtained in Example 1 (a) and Comparative Example (b) at 77 K. As can be seen from the figure, the pore size of the comparative sample and the compound is 0.62 nm.

[0021] Figure 4 The isotherms of the adsorption of methane and nitrogen by Example 1 and the comparative sample under normal temperature and pressure conditions are shown in the figure. As can be seen from the figure, the compound shows an adsorption amount of methane > nitrogen, which proves that the material has a preferential adsorption of methane.

[0022] Figure 5 : The adsorption heat of methane and nitrogen of Example 1 and the comparative sample. It can be seen from the figure 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 enhances the effect on methane.

[0023] Figure 6 The selectivity of Example 1 and the comparative sample to methane / nitrogen is shown in the figure. As can be seen from the figure, 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 a better selectivity to methane / nitrogen.

[0024] Figure 7 The dynamic breakthrough curves obtained for Example 1 (b) and Comparative Example (a) are shown in the figure. As can be seen from the figure, nitrogen breaks 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 objectives, features and advantages of the present invention, the scheme of the present invention will be further described below. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0026] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all of the embodiments.

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

[0028] The present invention further provides a method for preparing a chlorine-modified metal organic framework material, comprising the following steps:

[0029] Cobalt nitrate hexahydrate, α, β-di(4-pyridyl)ethylene glycol and 5-chloroisophthalic acid are dissolved in a solvent, and then the mixture is transferred to a reactor and reacted at 60-80°C for 12-48 hours; a pink powder is obtained by filtration and washed; finally, the powder is activated in a vacuum at 150-200°C for 6-12 hours to remove the solvent in the crystal pores to obtain a chlorine-modified metal organic framework material.

[0030] The present invention is a chlorine-modified metal organic framework material generated by a solvent thermal reaction under a solvent thermal environment using cobalt nitrate hexahydrate as a metal source, α, β-di(4-pyridyl)ethylene glycol and 5-chloroisophthalic acid as organic ligands. In the present invention, the solvent thermal reaction is carried out in an oven, and of course the reaction vessel of the solvent thermal reaction of the present invention is not limited to an oven.

[0031] In one embodiment provided by the present invention, the molar ratio of the cobalt nitrate hexahydrate, α, β-di(4-pyridyl)ethylene 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-di(4-pyridyl)ethylene glycol and 5-chloroisophthalic acid is 1:1:1.

[0032] In one embodiment provided by the present invention, 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. More preferably, the ratio is 1:1.

[0033] The invention also provides application of 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 invention are described in detail below.

[0036] Embodiment 1:

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

[0038] Table 1 shows the crystallographic parameters of the compounds prepared in Example 1

[0039] Table 1 Crystal data

[0040]

[0041]

[0042] Embodiment 2:

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

[0044] Embodiment 3:

[0045] Co(NO3)3·6H2O (0.75mmol), α, β-di(4-pyridyl)ethylene glycol (0.75mmol) and 5-chloroisophthalic acid (0.75mmol) were dissolved in a mixed solution of DMF / MeOH (1 / 1, 60mL), and then the mixture was transferred to a Teflon-lined stainless steel reactor and placed in an 80°C oven for reaction for 24h. After the reaction was completed, the mixed solution was cooled to room temperature and filtered to obtain the compound, which was then washed three times with fresh DMF and MeOH respectively. The obtained crystalline powder was vacuum dried at 180°C for 8 hours to obtain a chlorine-modified metal organic framework material.

[0046] Comparative Example (Preparation of Comparative Sample)

[0047] Co(NO3)3·6H2O (0.75mmol), α, β-di(4-pyridyl)ethylene glycol (0.75mmol) and isophthalic acid (0.75mmol) were dissolved in a mixed solution of DMF / MeOH (1 / 1, 60mL), and the mixture was transferred to a Teflon-lined stainless steel reactor and placed in a 70°C oven for reaction for 24h. After the reaction was completed, the mixed solution was cooled to room temperature and filtered to obtain the compound, which was then washed three times with fresh DMF and MeOH respectively. The obtained crystalline powder was vacuum dried at 180°C for 8 hours to obtain a metal organic framework material.

[0048] Test Example 1

[0049] Single gas adsorption test

[0050] About 130 mg of the control sample and the compound (the crystalline powder obtained in Example 1) were prepared respectively, and both were vacuum degassed at 453 K for 3-5 hours under high vacuum, and the N2 adsorption isotherm at 77 K was obtained using a Micromeritics ASAP 2460 instrument (the purity of the N2 used was 99.999%). The pore sizes of the control sample and the compound were analyzed using the DFT model, and the pore sizes of the control sample and the compound were both 0.62 nm, as shown in FIG. Figure 3 shown.

[0051] About 130 mg of the control sample and the compound (the crystalline powder obtained in Example 1) were prepared respectively. Both were vacuum degassed at 453 K for 5 hours under high vacuum. The CH4 and N2 adsorption isotherms at 298 K and 273 K were obtained using a Micromeritics ASAP 2460 instrument. The purity of the CH4 and N2 used was 99.999%. The adsorption data obtained are as follows: Figure 4 shown.

[0052] Test Example 2

[0053] Adsorption heat test:

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

[0055]

[0056] The adsorption heat of the reference sample and the compound is calculated, such as Figure 5 shown.

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

[0058] Optional testing:

[0059] In order to evaluate the gas separation ability of the sample, IAST calculation was performed on CH4 / N2 (50:50, v / v) adsorption based on the single gas adsorption isotherm obtained in Experimental Example 1. The selectivity of the comparative sample was 5.34, the selectivity of the compound was 9, and the selectivity was improved by 3.6. Figure 6 shown.

[0060] Dynamic penetration testing:

[0061] Dynamic penetration tests were performed on both the control sample and the compound. 0.6 g of the control sample and compound powder were placed in a stainless steel column, respectively, 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, a mixed gas CH4 / N2 (50:50, v / v) (flow rate: 10 mL / min) was introduced, and the outlet gas was analyzed by mass spectrometry. The data detected by the mass spectrometer were used to draw the Figure 7 It was found that the compound of Example 1 of the present invention had better separation performance than the control sample.

[0062] The above is only a specific implementation of the present invention, which enables those skilled in the art to understand or implement the present invention. Although detailed descriptions are given with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments, and they should all be covered by the protection scope of the claims.

Claims

1. A chlorine-modified metal organic framework material, characterized in that: The chemical formula is: C 20 H 16 ClCoN2O 6.5 ; Crystallographic data: belongs to orthorhombic system, space group Cmcm, unit 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, characterized in that: The following steps are involved: Cobalt nitrate hexahydrate, α, β-di(4-pyridyl)ethylene glycol and 5-chloroisophthalic acid are dissolved in a solvent, and then the mixture is transferred to a reactor and reacted at 60-80°C for 12-48 hours; a pink powder is obtained by filtration and washed; finally, it is activated in a vacuum at 150-200°C for 6-12 hours to remove the solvent in the crystal pores to obtain a chlorine-modified metal organic framework material.

3. The method for preparing a chlorine-modified metal organic framework material according to claim 2, characterized in that: The molar ratio of the cobalt nitrate hexahydrate, α, β-di(4-pyridyl)ethylene glycol and 5-chloroisophthalic acid is 1:0.5-1.5:0.50-1.

5.

4. The method for preparing a chlorine-modified metal organic framework material according to claim 3, characterized in that: The molar ratio of the cobalt nitrate hexahydrate, α, β-di(4-pyridyl)ethylene glycol and 5-chloroisophthalic acid is 1:1:

1.

5. The method for preparing a chlorine-modified metal organic framework material according to claim 2, characterized in that: The solvent is a mixed solvent of DMF and methanol.

6. The method for preparing a chlorine-modified metal organic framework material according to claim 5, characterized in that: The volume ratio of DMF to methanol in the mixed solvent is 0.8-1.2:

1.

7. Use of the chlorine-modified metal organic framework material according to claim 1 in methane / nitrogen adsorption separation.

8. Use of the chlorine-modified metal organic framework material prepared by the method for preparing a chlorine-modified metal organic framework material according to any one of claims 2 to 6 in methane / nitrogen adsorption separation.

9. The use according to claim 8, characterized in that The chlorine-modified metal organic framework material preferentially adsorbs methane in a methane / nitrogen mixer.

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