A MOF material NUC-200 and its preparation method and application

Abstract

The present invention relates to the field of gas separation technology, specifically to a MOF material NUC‑200 and a preparation method and application thereof. In order to solve the problem that the existing MOF material based on propylene / propane separation has adsorption selectivity and adsorption capacity that are difficult to balance, has poor structural stability and is expensive, the present invention provides a preparation method of a MOF material NUC‑200, comprising the following steps: 1) zinc acetate and 4,5‑dicyanoimidazole are sequentially added to methanol and stirred to dissolve; 2) ammonia water is added and stirred to produce a white solid precipitate; 3) the white solid precipitate is filtered, washed and dried to obtain a white solid adsorbent MOF material NUC‑200. The MOF material NUC‑200 described in the present invention is simple to prepare and has high production efficiency. At the same time, it has a high adsorption capacity for propylene and a high selectivity for propylene / propane, and can achieve efficient separation of a propylene / propane mixed gas.

Description

Technical Field

[0001] The present invention relates to the technical field of gas separation, and in particular to a MOF material NUC-200 and a preparation method and application thereof. Background Art

[0002] Propylene is the second largest chemical raw material after ethylene. With the rapid development of social modernization, the role of its downstream derivatives is increasing. At present, the main production processes of industrial propylene include catalytic cracking technology of by-product propylene, propylene co-production technology of cracking unit, propane dehydrogenation technology and methanol to olefins technology. The existing production technologies are all produced in the form of propylene mixtures, and polypropylene, which accounts for the largest proportion in the downstream, requires a raw material purity higher than 99.5%. Therefore, efficient separation of propylene is one of the important links in its production process. Among the many mixed impurities, propane is difficult to separate due to its similar physical properties to propylene. The current main separation technology is low-temperature distillation separation, which uses the difference in boiling point and relative volatility to separate. Propylene needs to be separated and purified in multiple steps, and the separation energy consumption is relatively high.

[0003] Under the current requirements of the "dual carbon" goal, seeking efficient and energy-saving separation technology is an urgent pursuit. Pressure swing adsorption technology stands out from many separation technologies with its many advantages such as low separation energy consumption, green environmental protection, and automated operation, and has important application value and prospects. At present, it is mainly limited by the development of high-efficiency adsorbents, and metal organic frameworks (MOFs) have the advantages of high specific surface area, pore size, and adjustable surface chemical environment. They can be used as an adsorbent construction platform to develop adsorbents with excellent performance for pressure swing adsorption technology, thereby achieving efficient separation of propylene / propane.

[0004] Although some progress has been made in the existing research on MOF materials based on propylene / propane separation, there are still problems such as difficulty in balancing adsorption selectivity and adsorption capacity, poor structural stability and high preparation cost. Summary of the invention

[0005] In order to solve the problems of the existing MOF materials based on propylene / propane separation, such as the difficulty in balancing the adsorption selectivity and adsorption capacity, the poor structural stability and the high preparation cost, the present invention provides a new MOF material NUC-200 and its preparation method and application.

[0006] The present invention is achieved by adopting the following technical solutions:

[0007] A MOF material NUC-200, whose chemical formula is (ZnC 13 H 13 N8O3) nIts crystal system belongs to the monoclinic system, the space group is P 21 / c, and the unit cell parameters are: a=11.8962(6) Å, b= 14.5975(5) Å, c=10.7904(4) Å, α= 90°, β=92.4099(15)°, γ= 90°.

[0008] A preparation method of a MOF material NUC-200 comprises the following steps: 1) adding zinc acetate and 4,5-dicyanoimidazole to methanol in sequence and stirring to dissolve; 2) adding ammonia water and stirring to continue the reaction for a period of time to produce a white solid precipitate; 3) filtering the white solid precipitate and washing it with methanol, and drying it to obtain a white solid adsorbent MOF material NUC-200.

[0009] Furthermore, the molar ratio of zinc acetate, 4,5-dicyanoimidazole, methanol and aqueous ammonia is 1:2:0.57:0.002.

[0010] Furthermore, in step 2), the stirring temperature is 0°C to 40°C.

[0011] Furthermore, in step 2), the stirring time is not less than 18 h.

[0012] The application of the MOF material NUC-200 described above in the separation of propylene / propane mixed gas includes the following separation steps: 1) passing the propylene / propane mixed gas into an adsorption column containing the activated MOF material NUC-200, and collecting high-purity propane at the outlet of the adsorption column; 2) collecting propylene adsorbed on the MOF material NUC-200 by vacuum desorption.

[0013] Furthermore, during the separation process, the flow rate, pressure and indoor temperature of the propylene / propane mixture remain unchanged.

[0014] Furthermore, the volume content of propylene in the propylene / propane mixed gas is 50-95%.

[0015] Furthermore, the pressure of the propylene / propane mixed gas when passing into the adsorption column was 1.01 bar, the flow rate was 1 mL / min, and the indoor temperature was 25°C.

[0016] Furthermore, a gas chromatograph is used to detect the purity of the gas at the outlet of the adsorption column, and gas collection is performed when it is confirmed that the gas is high-purity propane.

[0017] Furthermore, the adsorption column is a stainless steel adsorption column.

[0018] Furthermore, when the MOF material NUC-200 was activated, the activation temperature was 90°C and nitrogen was purged for 6 hours.

[0019] The beneficial effects of the present invention are as follows: the MOF material NUC-200 described in the present invention is synthesized by a stirring method, which is simple to prepare and has high production efficiency, and the organic ligand used is 4,5-dicyanoimidazole, which is inexpensive and has low preparation cost, and has a high adsorption capacity for propylene and a high propylene / propane selectivity, which can achieve efficient separation of propylene / propane mixed gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] 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.

[0021] 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 labor.

[0022] Figure 1 A schematic diagram of the three-dimensional structure of the MOF material NUC-200 prepared in the present invention;

[0023] Figure 2 This is the infrared spectrum of the MOF material NUC-200 prepared by the present invention, which is used to characterize the organic functional groups in the structure. The figure shows that the structure contains cyano and imine ester groups, which corresponds to the group changes after the alcoholysis of the ligand 4,5-dicyanoimidazole used. Half of the cyano groups in the original ligand are retained, and the other half are converted into imine ester groups;

[0024] Figure 3 The thermogravimetric curve of the MOF material NUC-200 prepared by the present invention shows that the structure has high thermal stability and can maintain structural integrity within 200°C, which can meet the operating conditions of adsorption separation technology in industry;

[0025] Figure 4 This is the single-component gas adsorption isotherm of the MOF material NUC-200 prepared in the present invention for the separation of propylene and propane at 298 K. It can be seen from the figure that NUC-200 shows an opening phenomenon for propylene, the opening pressure is about 0.1 bar, and the final propylene adsorption capacity reaches 55.4 cm 3 / g, but there is no opening phenomenon for propane, and its adsorption capacity is extremely low and close to zero adsorption, which indicates that NUC-200 has a large separation potential for propylene and propane mixed gas;

[0026] Figure 5This is the single-component gas adsorption isotherm of the MOF material NUC-200 prepared in the present invention for the separation of propylene and propane at 273 K. It can be seen from the figure that: the opening pressure of propylene is further reduced, and the adsorption capacity of propane is still very low, indicating that lowering the temperature is helpful to further improve the separation performance of the material for propylene / propane;

[0027] Figure 6 The MOF material NUC-200 prepared in the present invention is a separation curve of propylene / propane mixed gas of equal volume ratio at 273 K and normal pressure, indicating that the MOF material NUC-200 has a good propylene / propane dynamic separation effect;

[0028] Figure 7 The comparison diagram of the single-component gas adsorption isotherms of propylene and propane of the MOF material NUC-200 prepared by the present invention after proportional scale synthesis and the single-component gas adsorption isotherms of propylene and propane described in Example 1 shows that the material can still maintain the original adsorption selectivity and adsorption capacity after proportional scale expansion.

[0029] Figure 8 This is a test effect diagram of multiple single-component adsorption cycles of propylene by the MOF material NUC-200 prepared in the present invention, indicating that the adsorption performance of the MOF material NUC-200 does not decrease after multiple adsorption cycles, showing good cycle performance. DETAILED DESCRIPTION

[0030] 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.

[0031] In the description, it should be noted that the terms "first" and "second" are only used for descriptive purposes and should not be understood as indicating or implying relative importance. It should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be internal communication between two elements. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0032] 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.

[0033] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0034] A MOF material NUC-200, whose chemical formula is (ZnC 13 H 13 N8O3) n Its crystal system belongs to the monoclinic system, the space group is P 21 / c, and the unit cell parameters are: a=11.8962(6) Å, b= 14.5975(5) Å, c=10.7904(4) Å, α= 90°, β=92.4099(15)°, γ= 90°.

[0035] A preparation method of a MOF material NUC-200 comprises the following steps: 1) adding zinc acetate and 4,5-dicyanoimidazole to methanol in sequence and stirring to dissolve; 2) adding ammonia water and stirring to continue the reaction for a period of time to produce a white solid precipitate, wherein the molar ratio of zinc acetate, 4,5-dicyanoimidazole, methanol and ammonia water is 1:2:0.57:0.002, the stirring temperature after adding ammonia water is 0°C-40°C, and the stirring time is not less than 18 h; 3) filtering the white solid precipitate and washing it with methanol, and drying it to obtain a white solid adsorbent MOF material NUC-200.

[0036] A use of a MOF material NUC-200 in separation of a propylene / propane mixed gas comprises the following separation steps: 1) passing the propylene / propane mixed gas into a stainless steel tube adsorption column containing the activated MOF material NUC-200, wherein when the MOF material NUC-200 is activated, the activation temperature is 90°C, nitrogen is used for 6 hours, the pressure of the propylene / propane mixed gas when passing into the adsorption column is 1.01 bar, the flow rate is 1 mL / min, and the indoor temperature is 25°C. Meanwhile, during the separation process, the flow rate, pressure and indoor temperature of the propylene / propane mixed gas remain unchanged, and then a gas chromatograph is used to detect the gas purity at the outlet of the adsorption column, and the gas is collected when it is confirmed that the gas is high-purity propane; 2) the propylene adsorbed on the MOF material NUC-200 is collected by a vacuum desorption method.

[0037] The performance of the MOF material NUC-200 prepared above was tested and the following results were obtained: 1) Figure 1 and Figure 2 As shown in the figure, the MOF material NUC-200 has a three-dimensional structure formed by the stacking of one-dimensional chain phases, and its pores are rich in polar groups such as cyano and imine ester groups, which have a stronger interaction with propylene with greater polarity; 2) The material has high thermal stability and can maintain structural integrity within 200°C, which can meet the operating conditions of adsorption separation technology in industry, such as Figure 33) The material itself has a certain degree of flexibility. NUC-200 shows an opening phenomenon for propylene, and the opening pressure is about 0.1 bar. The final propylene adsorption capacity reaches 55.4 cm 3 / g, but there is no opening phenomenon for propane, and its adsorption capacity is extremely low and close to zero adsorption, which shows that NUC-200 has great separation potential for propylene and propane mixed gas, has high propylene / propane selectivity, and can achieve efficient separation of propylene / propane based on flexible dynamic screening mechanism, such as Figure 4 and 5 As shown; 4) As Figure 6 As shown in the figure, the dynamic separation test further proves that the material achieves efficient separation of propylene / propane mixed gas, that is, propane quickly passes through the adsorption column, and high-purity propane can be collected as determined by gas chromatography, and propylene is adsorbed by the adsorbent in the adsorption column until it starts to pass through at 75 minutes; 5) In addition, after the large-scale synthesis of NUC-200, its propylene adsorption capacity and adsorption selectivity did not decrease, as shown in Figure 7 As shown; 6) As Figure 8 As shown, the material has excellent recycling performance. Combining the above advantages, MOF adsorbent NUC-200 has high application value and prospects for industrial propylene separation.

[0038] 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 MOF material NUC-200, characterized in that: Its chemical formula is (ZnC 13 H 13 N8O3) n Its crystal system belongs to the monoclinic system, the space group is P 21 / c, the unit cell parameters are: a=11.8962(6) Å, b= 14.5975(5) Å, c=10.7904(4) Å, α= 90°, β= 92.4099(15)°, γ= 90°.

2. The method for preparing a MOF material NUC-200 according to claim 1, characterized in that: The method comprises the following steps: 1) adding zinc acetate and 4,5-dicyanoimidazole to methanol in sequence and stirring to dissolve; 2) adding ammonia water and stirring to continue the reaction for a period of time to produce a white solid precipitate; 3) filtering the white solid precipitate and washing it with methanol, and drying it to obtain a white solid adsorbent MOF material NUC-200.

3. The method for preparing a MOF material NUC-200 according to claim 2, characterized in that: The molar ratio of zinc acetate, 4,5-dicyanoimidazole, methanol and aqueous ammonia is 1:2:0.57:0.

002.

4. The method for preparing a MOF material NUC-200 according to claim 3, characterized in that: In step 2), the stirring temperature is 0°C to 40°C.

5. The method for preparing a MOF material NUC-200 according to claim 3, characterized in that: In step 2), the stirring time is not less than 18 h.

6. Application of MOF material NUC-200 in separation of propylene / propane mixed gas, characterized in that: The MOF material NUC-200 is the MOF material NUC-200 described in claim 1.

7. The use of a MOF material NUC-200 in separation of propylene / propane mixed gas according to claim 6, characterized in that: Specifically, the separation steps include: 1) passing the propylene / propane mixed gas into an adsorption column containing the activated MOF material NUC-200, and collecting high-purity propane at the outlet of the adsorption column; 2) collecting the propylene adsorbed on the MOF material NUC-200 by vacuum desorption.

8. The use of a MOF material NUC-200 according to claim 7 in separation of propylene / propane mixed gas, characterized in that: The pressure of the propylene / propane mixture when passing into the adsorption column was 1.01 bar, the flow rate was 1 mL / min, and the room temperature was 25 °C.

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