Adsorbent material NUC-201Cu as well as preparation method and application thereof

Abstract

The invention relates to the technical field of gas separation, in particular to an adsorbent material NUC-201Cu and a preparation method and application thereof. The invention aims to provide an adsorbent material capable of effectively improving the separation efficiency of methane / nitrogen, namely a preparation method of the adsorbent material NUC-201Cu, which comprises the following steps: 1) sequentially adding copper chloride, 4, 5-dicyanoimidazole, sodium azide and fluoboric acid into a mixed solvent of acetonitrile and water, and stirring for dissolving to form a mixed solution; the invention relates to a preparation method of a solid adsorbent material NUC-201Cu, which comprises the following steps: 1) preparing a mixed solution, 2) putting the mixed solution formed in the step 1) into a drying oven until a solid precipitate is obtained, and 3) filtering the obtained solid precipitate, washing with a mixed solvent of acetonitrile and water, and drying to obtain the solid adsorbent material NUC-201Cu. The adsorption material prepared by the method has excellent methane / nitrogen separation performance.

Description

Technical Field

[0001] The present invention relates to the technical field of gas separation, and in particular to an adsorbent material NUC-201Cu, a preparation method thereof, and an application thereof. Background Art

[0002] As an important clean energy gas, methane has significant advantages in replacing traditional fossil fuels, alleviating energy crises and reducing environmental pollution due to its high calorific value combustion characteristics and low carbon emissions. As an important unconventional natural gas resource, the development and utilization of low-concentration coalbed methane can effectively supplement the global high-quality methane resources. However, its development and utilization are currently severely restricted by nitrogen. The presence of associated nitrogen significantly reduces the combustion calorific value of low-concentration coalbed methane (low-concentration coalbed methane with associated nitrogen is also referred to as methane / nitrogen mixed gas in this application). On the other hand, the direct emission of such low-concentration coalbed methane without treatment not only causes energy waste, but also exacerbates the greenhouse effect (the greenhouse effect of methane is 21 times that of carbon dioxide). Therefore, the development of efficient and economical methane / nitrogen separation technology to achieve high-value utilization of low-concentration coalbed methane is of great significance for optimizing the energy structure and reducing environmental pollution.

[0003] Methane and nitrogen are extremely challenging to separate due to their highly similar physicochemical properties and similar molecular kinetic sizes. Pressure swing adsorption (PSA) is considered one of the most promising solutions for methane / nitrogen separation due to its operational flexibility, environmental friendliness, and low energy consumption. Its core technology lies in the design and development of high-performance adsorbents. Currently, this is primarily limited by the development of efficient adsorbents. Metal-organic frameworks (MOFs) are widely used in methane / nitrogen separation due to their large surface area, diverse structural diversity, and specifically tunable adsorption environments. Current research focuses on manipulating the pore adsorption environment, including constructing pore structures that match the size of methane molecules and manipulating the pore surface chemistry to increase methane adsorption sites. Although MOF materials have achieved significant progress in methane / nitrogen separation, they are still limited by the interplay between adsorption capacity and selectivity, as well as poor structural stability. Further improvements in methane / nitrogen separation efficiency are urgently needed. Summary of the Invention

[0004] The object of the present invention is to provide an adsorbent material that can effectively improve the separation efficiency of methane / nitrogen, namely an adsorbent material NUC-201Cu and its preparation method and application.

[0005] The present invention is achieved by adopting the following technical solutions: An adsorbent material NUC-201Cu, whose structural formula is Cu2(N 10C6H2)2, space group is P21, unit cell parameters are: a=8.68025 Å, b=9.13998Å, c=14.71573Å, α= 90°, β= 89.9977°, γ = 90°.

[0006] A preparation method of an adsorbent material NUC-201Cu comprises the following steps: 1) adding copper chloride, 4,5-dicyanoimidazole, sodium azide, and fluoroboric acid to a mixed solvent of acetonitrile and water in sequence and stirring to dissolve the mixture to form a mixed solution; 2) placing the mixed solution formed in step 1) in an oven until a blue solid precipitate is obtained; and 3) filtering the obtained blue solid precipitate, washing it with a mixed solvent of acetonitrile and water, and drying it to obtain the blue solid adsorbent material NUC-201Cu.

[0007] Furthermore, in step 1), the molar ratio of 4,5-dicyanoimidazole, copper chloride, sodium azide, acetonitrile, water, and fluoroboric acid is 4:15:15:4:22:0.2.

[0008] Furthermore, in step 2), the oven temperature is 100° C. and the reaction time is 3 days.

[0009] Furthermore, in step 3), the filtered blue solid precipitate is washed three times with a mixed solvent of acetonitrile and water, wherein the volume of acetonitrile and water is 1:2.

[0010] The invention discloses an adsorbent material NUC-201Cu for separating methane / nitrogen mixed gas. The methane / nitrogen mixed gas comes into contact with NUC-201Cu, and the methane / nitrogen are separated by adsorption.

[0011] An adsorbent material NUC-201Cu is used in the separation of a methane / nitrogen mixture. The specific steps of the separation include: 1) passing the methane / nitrogen mixture into an adsorption column filled with activated NUC-201Cu, and directly collecting high-purity nitrogen at the outlet; 2) collecting methane adsorbed by the NUC-201Cu by vacuum desorption.

[0012] Furthermore, in the specific step 1) of separation, the pressure of the methane / nitrogen mixture when passing into the adsorption column is 1.01 bar, the temperature is 0°C or 25°C, and the flow rate is 1 mL / min, 2 mL / min, or 3 mL / min.

[0013] The beneficial effects of the present invention are as follows: 1) The novel MOF material NUC-201Cu prepared by the present invention uses 4,5-dicyanoimidazole organic ligand as a reaction precursor, and realizes the conversion of cyano group to tetrazole group in a one-pot in-situ reaction process, thereby producing a novel copper-based MOF named NUC-201Cu. At the same time, dual optimization of the pore environment is achieved during the framework assembly process, firstly, electron-rich tetrazole adsorption sites are introduced to enhance methane adsorption, and secondly, Cu 2+ 1) The strong coordination ability of NUC-201Cu optimizes the pore size to match methane, resulting in excellent methane adsorption capacity and improved adsorption selectivity. 2) Dynamic separation tests further demonstrated that the material effectively enhanced methane / nitrogen separation performance. 3) The high structural stability of NUC-201Cu enables excellent recyclability. These advantages indicate that the adsorbent material NUC-201Cu has high application value and prospects in industrial methane separation. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] 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.

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0016] Figure 1 The three-dimensional structure of NUC-201Cu prepared in this invention has a space group of P21, Cu 2+ The center is five-coordinated, coordinated with three organic ligands respectively. Correspondingly, each organic ligand provides five nitrogen atom coordination sites, which are coordinated with three Cu 2+ The framework contains one-dimensional, approximately square pores, in which tetrazole groups formed by in-situ conversion of cyano groups are distributed, which can form strong interactions with methane. Figure 2 This is the PXRD refinement pattern of the adsorbent material NUC-201Cu. The relevant refinement parameters are shown in the figure. The structural information of NUC-201Cu, including space group, coordination mode, coordination number, and topological structure, was obtained through PXRD refinement. Figure 3Figure 2 is the PXRD pattern of the adsorbent material NUC-201Cu in the embodiment of the present invention and the NUC-201Zn in the comparative example. The data in the figure show that the PXRD patterns of the two MOF materials correspond well to the corresponding theoretical simulation patterns and have no impurity peaks, which indicates that the prepared materials are pure and free of impurities. Figure 4 Thermogravimetric curves of the adsorbent material NUC-201Cu in the embodiment of the present invention and NUC-201Zn in the comparative example are shown. The test data show that both materials have high structural stability and remain stable within 300°C, meeting the requirements of industrial pressure swing adsorption separation technology. Figure 5 The single-component gas adsorption isotherm of carbon dioxide on the adsorbent material NUC-201Zn at 273 K is used to obtain the pore size distribution information; Figure 6 The single-component gas adsorption isotherm of carbon dioxide on the adsorbent material NUC-201Cu at 273 K is used to obtain pore size distribution information; Figure 7 The pore size distribution diagram of the adsorbent material NUC-201Cu in the embodiment of the present invention and NUC-201Zn in the comparative example is shown in the figure. It can be seen from the figure that the pore size of NUC-201Cu is mainly distributed around 6.9 Å, which is slightly larger than the pore size distribution of NUC-201Zn at 6.5 Å. This indicates that in the NUC-201 structure, the metal ions are composed of Zn 2+ Replaced by Cu 2+ , through Cu 2+ The strong coordination ability of the pores further optimizes the pore shape, which is beneficial to improve the adsorption of methane; Figure 8 The single-component adsorption-desorption isotherms of methane and nitrogen of the adsorbent material NUC-201Zn described in the comparative example at 273 K and 298 K. The adsorption capacity of methane at 298 K and 1 bar reaches 30 cm 3 / g, and the adsorption capacity for nitrogen reaches 9.3 cm 3 / g, showing a large adsorption difference for methane / nitrogen adsorption; Figure 9 The single-component adsorption-desorption isotherms of methane and nitrogen for the adsorbent material NUC-201Cu described in the embodiment of the present invention at 273 K and 298 K. The adsorption capacity of methane at 298 K and 1 bar reaches 36 cm 3 / g, which is higher than 5A molecular sieve and NUC-201Zn, and the adsorption capacity of nitrogen reaches 12.1 cm 3 / g, showing a large adsorption difference for methane / nitrogen adsorption; Figure 10 Figure 3 shows the IAST selectivity of the adsorbent materials NUC-201Cu in the examples of the present invention and NUC-201Zn in the comparative example for a methane / nitrogen (1 / 4 volume ratio) mixture at 298 K, calculated based on single-component adsorption isotherm data for methane and nitrogen. The figure shows that both adsorbent materials have high methane / nitrogen selectivity, with NUC-201Cu showing a 32% improvement in selectivity relative to NUC-201Zn. Figure 11 This is the infrared spectrum of the in situ methane adsorption of the adsorbent material NUC-201Cu described in the present invention. As shown, when the in situ activated NUC-201Cu was subjected to methane adsorption, two characteristic absorption peaks rapidly appeared at 1200 cm⁻¹ (corresponding to the CH bending vibration) and 3000 cm⁻¹ (attributed to the CH stretching vibration). In a nitrogen control experiment conducted under the same experimental conditions, no significant characteristic absorption signals were detected. This directly confirms the presence of active sites in the NUC-201Cu framework that specifically interact with methane molecules, fully demonstrating the material's preferential adsorption capacity for methane molecules. Figure 12 The dynamic separation curves of the adsorbent materials NUC-201Cu in the embodiment of the present invention and NUC-201Zn in the comparative example for a methane / nitrogen (volume ratio of 1 / 4) mixed gas at 298 K and 1 bar are shown; Figure 13 Dynamic separation curves of adsorbent material NUC-201Cu at 298 K and 1 bar with a methane / nitrogen (volume ratio of 1 / 4) mixed gas flow rate of 1 mL / min, 2 mL / min, and 3 mL / min, respectively; Figure 14 The dynamic separation curves of the adsorbent material NUC-201Cu at different temperatures under the conditions of 1 bar and a methane / nitrogen (volume ratio of 1 / 4) mixed gas flow rate of 1 mL / min; Figure 15 The cyclic dynamic separation curve of the adsorbent material NUC-201Cu under the conditions of 298 K and 1 bar, with a methane / nitrogen (volume ratio of 1 / 4) mixed gas flow rate of 1 mL / min, shows that NUC-201Cu has a good cycle life; Figure 16 This is the methane adsorption isotherm diagram of the adsorbent material NUC-201Cu after different stability tests. The adsorption data shows that the methane adsorption performance of NUC-201Cu remains basically unchanged, showing good structural stability. DETAILED DESCRIPTION

[0017] 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, in the absence of conflict, the embodiments of the present invention and the features therein can be combined with each other.

[0018] In the description, it should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance. It should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood broadly. For example, they can refer to fixed connections, removable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms based on specific circumstances.

[0019] 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 the embodiments.

[0020] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0021] An embodiment of the present invention: A method for preparing an adsorbent material NUC-201Cu, comprising the following steps: 1) adding 0.75 mmol of copper chloride, 0.2 mmol of 4,5-dicyanoimidazole, 0.75 mmol of sodium azide, and 0.01 mmol of fluoroboric acid in sequence to a mixed solvent of 0.2 mmol of acetonitrile and 1.1 mmol of water and stirring to dissolve the mixture to form a mixed solution; 2) placing the mixed solution formed in step 1) in an oven until a solid precipitate is obtained, wherein the oven temperature is 100°C and the reaction time is 3 days; 3) filtering the obtained solid precipitate and washing it three times with a mixed solvent of acetonitrile and water, wherein the volume of acetonitrile and water is 1:2, and drying to obtain the solid adsorbent material NUC-201Cu.

[0022] The NUC-201Cu prepared in this example was loaded into a 4 x 110 mm stainless steel adsorption column. An external temperature controller maintained the adsorbent's ambient temperature at 200°C. Helium was then purged for 10 hours to remove solvent molecules from the adsorbent's pores. After the activation process, the separation temperature was set to 25°C. The outlet pressure of the methane / nitrogen mixture was adjusted to 1.01 bar using a pressure reducing valve, and the flow rate was controlled at 1 mL / min using a mass flow meter. The methane / nitrogen mixture was then introduced into the adsorption column containing the adsorbent material. The gas composition was measured at the outlet of the separation device using a Shimadzu gas chromatograph equipped with a BID detector.

[0023] Comparative Example: A method for preparing an adsorbent material NUC-201Zn, comprising the following steps: 1) adding 0.75 mmol of zinc chloride, 0.2 mmol of 4,5-dicyanoimidazole, 0.75 mmol of sodium azide, and 0.01 mmol of fluoroboric acid in sequence to a mixed solvent of 0.2 mmol of acetonitrile and 1.1 mmol of water and stirring to dissolve the mixture to form a mixed solution; 2) placing the mixed solution formed in step 1) in an oven until a solid precipitate is obtained, wherein the oven temperature is 100°C and the reaction time is 3 days; 3) filtering the obtained solid precipitate and washing it three times with a mixed solvent of acetonitrile and water, wherein the volume of acetonitrile and water is 1:2, and drying to obtain the solid adsorbent material NUC-201Zn.

[0024] The NUC-201Zn prepared in the comparative example was loaded into a 4 x 110 mm stainless steel adsorption column. The adsorbent's ambient temperature was maintained at 200°C using an external temperature controller. Helium was then purged for 10 hours to remove solvent molecules from the adsorbent's pores. After the activation process, the separation temperature was set at 25°C. The outlet pressure of the methane / nitrogen mixture was adjusted to 1.01 bar using a pressure reducing valve, and the flow rate was controlled at 1 mL / min using a mass flow meter. The methane / nitrogen mixture was then introduced into the adsorption column containing the adsorbent material. The gas composition was measured at the outlet of the separation device using a Shimadzu gas chromatograph equipped with a BID detector.

[0025] The performance comparison of the adsorbent materials prepared in the examples of the present invention and the comparative examples shows that the adsorbent material NUC-201Cu has excellent methane / nitrogen separation performance and is better than that of the adsorbent material NUC-201Zn. Figure 1-16 shown.

[0026] The above description is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Although detailed descriptions have been made with reference to the aforementioned embodiments, those skilled in the art should understand that they may still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents; and such modifications or replacements do not deviate from the essence of the corresponding technical solutions within the scope of the technical solutions of the embodiments, and they should all be included in the scope of protection of the claims.

Claims

1. An adsorbent material NUC-201Cu, characterized in that: Its structural formula is Cu2(N 10 C6H2)2, space group is P21, unit cell parameters are: a=8.68025 Å, b=9.13998Å, c=14.71573Å, α=90°, β=89.9977°, γ =90°.

2. The method for preparing an adsorbent material NUC-201Cu according to claim 1, characterized in that: The method comprises the following steps: 1) adding copper chloride, 4,5-dicyanoimidazole, sodium azide and fluoroboric acid to a mixed solvent of acetonitrile and water in sequence and stirring to dissolve the mixture to form a mixed solution; 2) placing the mixed solution formed in step 1) in an oven until a solid precipitate is obtained; 3) filtering the obtained solid precipitate, washing it with a mixed solvent of acetonitrile and water, and drying it to obtain a solid adsorbent material NUC-201Cu.

3. The method for preparing the adsorbent material NUC-201Cu according to claim 2, characterized in that: In step 1), the molar ratio of 4,5-dicyanoimidazole, copper chloride, sodium azide, acetonitrile, water, and fluoroboric acid is 4:15:15:4:22:0.

2.

4. The method for preparing the adsorbent material NUC-201Cu according to claim 3, characterized in that: The oven temperature in step 2) is 100°C and the reaction time is 3 days.

5. The method for preparing the adsorbent material NUC-201Cu according to claim 4, characterized in that: In step 3), the filtered solid precipitate is washed three times with a mixed solvent of acetonitrile and water, wherein the volume of acetonitrile and water is 1:

2.

6. Application of an adsorbent material NUC-201Cu in separation of methane / nitrogen mixed gas, characterized in that: The methane / nitrogen mixture is brought into contact with the NUC-201Cu, and the methane / nitrogen separation is achieved by adsorption.

7. Application of an adsorbent material NUC-201Cu in separation of methane / nitrogen mixed gas, characterized in that: The specific steps of separation include the following: 1) passing a methane / nitrogen mixture into an adsorption column filled with activated NUC-201Cu and directly collecting high-purity nitrogen at the outlet; 2) collecting the methane adsorbed by NUC-201Cu by vacuum desorption.

8. Use of the adsorbent material NUC-201Cu in separation of methane / nitrogen mixed gas according to claim 7, characterized in that: In step 1), the pressure of the methane / nitrogen mixture when passing into the adsorption column is 1.01 bar, the temperature is 0°C or 25°C, and the flow rate is 1 mL / min, 2 mL / min, or 3 mL / min.

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