Application of a MOF material NUC-200 in the separation of carbon dioxide / methane and carbon dioxide / nitrogen mixed gases

Abstract

The present invention relates to the field of gas separation technology, and specifically to the application of a MOF material NUC-200 in the separation of carbon dioxide / methane and carbon dioxide / nitrogen mixtures. In order to solve the problems of high regeneration energy consumption of existing adsorbents for separating carbon dioxide mixtures and poor structural stability of the adsorbents in humid environments, the present invention provides an application of a MOF material NUC-200 in the separation of carbon dioxide / methane and carbon dioxide / nitrogen mixtures, wherein the preparation method of the MOF material NUC-200 comprises the following steps: 1) adding zinc acetate and 4,5-dicyanoimidazole to methanol and stirring; 2) adding ammonia water and stirring to continue the reaction until a white solid precipitate appears; 3) filtering, washing, and drying the white solid precipitate. The MOF material NUC-200 described in the present invention can achieve efficient separation of carbon dioxide / methane and carbon dioxide / nitrogen mixtures.

Description

Technical Field

[0001] The present invention relates to the technical field of gas separation, and specifically to the application of a MOF material NUC-200 in the separation of carbon dioxide / methane and carbon dioxide / nitrogen mixed gases. Background Art

[0002] The primary energy sources used for global economic development today include fossil fuels such as coal, oil, and natural gas. Due to their limited reserves and non-renewable nature, fossil fuels are becoming increasingly scarce with the rapid development of human society, leading to an energy shortage crisis. Biogas, including biogas, can serve as an important supplement to fossil fuels. The main components of biogas are methane and carbon dioxide, both greenhouse gases. If released directly into the atmosphere without proper utilization, this can further exacerbate the greenhouse effect. Biogas contaminated with carbon dioxide can also affect its development and utilization, so the separation of carbon dioxide and methane is necessary before biogas development and utilization. Furthermore, conventional natural gas pipeline transportation also requires the removal of any carbon dioxide impurities. This is because the presence of carbon dioxide not only reduces the calorific value of natural gas but also corrodes pipelines. Therefore, natural gas must undergo carbon dioxide removal before transportation. Therefore, both conventional natural gas transportation and biogas development and utilization currently involve the separation of carbon dioxide / methane mixtures.

[0003] In addition, large amounts of carbon dioxide are emitted from industries such as thermal power generation, steel, and cement. Carbon dioxide capture, utilization, and storage (CCUS) is a powerful way to reduce carbon dioxide emissions. Post-combustion carbon dioxide capture involved in CCUS is considered to be one of the most important technical routes to achieve carbon dioxide emission reduction in the above-mentioned industries. The separation target is mainly the separation of carbon dioxide / nitrogen mixtures.

[0004] Therefore, achieving high-efficiency methane purification and utilizing carbon dioxide capture is of great significance to current social and economic development and mitigating the greenhouse effect to achieve the "dual carbon goals".

[0005] The more mature low-temperature distillation technology in the industry requires separation in high-pressure, low-temperature, multi-step distillation towers, and the separation energy consumption is extremely high; although the solvent absorption technology has high selectivity and high removal depth, it has a series of problems such as solvent treatment and equipment corrosion; membrane separation technology occupies a small area and is flexible to operate, but its selectivity is insufficient, the separation purity is low, and large-scale membrane production processes still need further research and development, which limits its application; and the pressure swing adsorption technology with adsorbent as the core has extremely important application value and prospects for the advantages of high adsorption selectivity of mixed gases, high purity of separated product gases, green environmental protection, and low separation energy consumption. The key to pressure swing adsorption technology is to prepare or select high-efficiency adsorbents that have both adsorption capacity and adsorption selectivity, low preparation cost, good structural stability, and long cycle life.

[0006] Metal-organic frameworks (MOFs) have been widely used to construct high-efficiency adsorbents to solve the above-mentioned separation problems due to their many advantages, such as high specific surface area, adjustable pore size, and easy functional modification of the pore surface. Conventional introduction of unsaturated metal sites and amino surface modification can significantly improve the carbon dioxide adsorption capacity, but due to the high adsorption heat of the adsorbent, subsequent vacuum desorption of the adsorbed gas is difficult, that is, heating may be required, and the energy consumption of the adsorbent regeneration is high. Relevant content is described in the literature McDonald TM, Lee WR, Mason JA, et al.Capture of carbon dioxide from air and flue gas in the alkylamine-appended metal-organicframework mmen-Mg2(dobpdc).[J].Journal of the American Chemical Society,2012, 134(16):7056.DOI:10.1021 / ja300034j. At the same time, this type of adsorbent has poor structural stability in a humid environment, which will significantly reduce the separation performance of the adsorbent. Summary of the Invention

[0007] In order to solve the problems of high regeneration energy consumption of existing adsorbents used to separate carbon dioxide mixed gases and poor structural stability of the adsorbents in humid environments, the present invention provides a new application of MOF material NUC-200 in the separation of carbon dioxide / methane and carbon dioxide / nitrogen mixed gases.

[0008] The present invention is achieved by adopting the following technical solutions:

[0009] A MOF material NUC-200 is used in the separation of a carbon dioxide / methane mixture. The preparation method of the MOF material NUC-200 includes the following steps: 1) zinc acetate and 4,5-dicyanoimidazole are sequentially added to methanol and stirred to dissolve to form a mixed solution; 2) ammonia water is added to the mixed solution, and the mixture is stirred and reacted for a period of time to produce a white solid precipitate; 3) the white solid precipitate is filtered, washed with methanol, and dried to obtain a white solid adsorbent MOF material NUC-200.

[0010] Furthermore, the molar ratio of zinc acetate, 4,5-dicyanoimidazole, methanol, and aqueous ammonia is 1:2:0.57:0.002.

[0011] Furthermore, in step 2) of the preparation method of MOF material NUC-200, in step 2), the stirring temperature is 0°C~40°C, and the stirring time is not less than 18 h.

[0012] Furthermore, the specific steps of using the MOF material NUC-200 to separate a carbon dioxide / methane mixture include the following: 1) passing carbon dioxide / methane into an adsorption column containing the activated MOF material NUC-200, and directly collecting high-purity methane at the outlet; 2) collecting the carbon dioxide adsorbed by the MOF material NUC-200 by vacuum desorption.

[0013] Furthermore, in the specific step 1) of separation, the pressure of the carbon dioxide / methane mixture when passing into the adsorption column is 1.01 bar, the flow rate is 1 mL / min, and the indoor temperature is 25°C.

[0014] A MOF material NUC-200 is used in the separation of a carbon dioxide / nitrogen mixture. The preparation method of the MOF material NUC-200 includes the following steps: 1) zinc acetate and 4,5-dicyanoimidazole are sequentially added to methanol and stirred to dissolve to form a mixed solution; 2) ammonia water is added to the mixed solution, and the mixture is stirred and reacted for a period of time to produce a white solid precipitate; 3) the white solid precipitate is filtered, washed with methanol, and dried to obtain a white solid adsorbent MOF material NUC-200.

[0015] Furthermore, the molar ratio of zinc acetate, 4,5-dicyanoimidazole, methanol, and aqueous ammonia is 1:2:0.57:0.002.

[0016] Furthermore, in step 2) of the preparation method of MOF material NUC-200, in step 2), the stirring temperature is 0°C~40°C, and the stirring time is not less than 18 h.

[0017] Furthermore, the specific steps of using the MOF material NUC-200 to separate a carbon dioxide / nitrogen mixture include the following: 1) passing carbon dioxide / nitrogen into an adsorption column containing the activated MOF material NUC-200, and directly collecting high-purity methane at the outlet; 2) collecting the carbon dioxide adsorbed by the MOF material NUC-200 by vacuum desorption.

[0018] Furthermore, in the specific step 1) of separation, the pressure of the carbon dioxide / nitrogen mixture when passing into the adsorption column is 1.01 bar, the flow rate is 1 mL / min, and the indoor temperature is 25°C.

[0019] The beneficial effects of the present invention are as follows: 1) The MOF material NUC-200 of the present invention, prepared by a room temperature stirring method, is a microporous three-dimensional structure formed by stacking one-dimensional chains. During the synthesis process, the original ligand 4,5-dicyanoimidazole undergoes alcoholysis, and some cyano groups are converted into imine ester groups. Therefore, abundant polar groups cyano and imine ester groups are distributed in the narrow pore structure, which can form a strong interaction with carbon dioxide with greater polarity; 2) Single-component adsorption isotherms show that the MOF material NUC-200 achieves size screening of carbon dioxide / methane and carbon dioxide / nitrogen, and has high adsorption selectivity and adsorption ratio; 3) Dynamic separation tests show that the co-adsorption time of the material is almost zero, methane or nitrogen quickly passes through the adsorption column, while carbon dioxide has a longer penetration time, achieving efficient separation of carbon dioxide / methane and carbon dioxide / nitrogen mixtures; 4) The material has excellent carbon dioxide adsorption and recycling performance, and does not lose its original carbon dioxide adsorption performance even after long-term storage and in a certain humidity environment; 5) The material has low adsorption heat and low regeneration energy consumption. 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 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.

[0022] Figure 1 The single-component adsorption isotherm of carbon dioxide for the MOF material NUC-200 prepared in the present invention at 298 K. From the adsorption data, it can be determined that the MOF material NUC-200 after scaled-up synthesis will not lose its carbon dioxide adsorption performance;

[0023] Figure 2 The single-component adsorption isotherms of carbon dioxide for the MOF material NUC-200 synthesized at different stirring temperatures at 298 K show that controlling the synthesis temperature within 40°C can ensure the adsorption performance of carbon dioxide for the NUC-200 adsorbent.

[0024] Figure 3This is the single-component gas adsorption isotherm of the MOF material NUC-200 for carbon dioxide, methane, and nitrogen at 273 K. The figure shows that the material exhibits a high carbon dioxide adsorption capacity in the low-pressure region, indicating that the structure has a strong adsorption force for carbon dioxide. The adsorption capacity is significantly higher than that of methane and nitrogen, and the adsorption capacity of methane and nitrogen is extremely low, indicating that the material can achieve efficient separation of carbon dioxide / methane and carbon dioxide / nitrogen mixtures based on size screening.

[0025] Figure 4 This is the single-component gas adsorption isotherm of the MOF material NUC-200 for carbon dioxide, methane, and nitrogen at 298 K. The figure shows that the material adsorbs more carbon dioxide than methane and nitrogen, indicating that the material has a strong adsorption affinity for carbon dioxide and has high potential for separating carbon dioxide / methane and carbon dioxide / nitrogen mixtures.

[0026] Figure 5 This is the single-component gas adsorption isotherm of the MOF material NUC-200 for carbon dioxide, methane, and nitrogen at 313 K. The figure shows that the material's adsorption capacity for carbon dioxide is still higher than that for methane and nitrogen, indicating that the material has the potential to separate carbon dioxide / methane mixtures and carbon dioxide / nitrogen at higher temperatures.

[0027] Figure 6 This is the separation curve of the MOF material NUC-200 for a mixture of carbon dioxide and methane in equal volume ratio at room temperature and normal pressure;

[0028] Figure 7 This is the separation curve of the MOF material NUC-200 for a mixture of carbon dioxide and nitrogen in equal volume ratio at room temperature and normal pressure;

[0029] Figure 8 This is the carbon dioxide single-component gas adsorption isotherm of the MOF material NUC-200 after being placed in the environment for different periods of time. Compared with the original synthesized material, the structure of this material is not damaged and the carbon dioxide adsorption performance does not decrease after being placed in the indoor environment for a long time.

[0030] Figure 9 This is the single-component gas adsorption isotherm of carbon dioxide after the MOF material NUC-200 was placed in environments with different relative humidity. As can be seen from the figure, its carbon dioxide adsorption performance did not decrease, indicating that its structural stability is good;

[0031] Figure 10 This is a carbon dioxide adsorption cycle test diagram of the MOF material NUC-200. After multiple cycle tests, it can still maintain its original adsorption performance;

[0032] Figure 11The adsorption-desorption isotherm of CO2 of MOF material NUC-200 at 298 K shows that the MOF material NUC-200 can be directly desorbed in vacuum;

[0033] Figure 12 This is the adsorption heat diagram of MOF material NUC-200 for CO2. The adsorption heat of NUC-200 for CO2 is around 30 kJ / mol when it is close to zero adsorption, indicating that the adsorption heat of this material for CO2 is low, which is conducive to low-energy regeneration of the adsorbent. DETAILED DESCRIPTION

[0034] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the solutions 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.

[0035] 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.

[0036] 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.

[0037] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0038] Example 1: Application of a MOF material NUC-200 in the separation of carbon dioxide / methane mixed gas, wherein the preparation method of the MOF material NUC-200 comprises the following steps: 1) zinc acetate and 4,5-dicyanoimidazole are added to methanol in sequence and stirred to dissolve to form a mixed solution; 2) ammonia water is added to the mixed solution and stirred and reacted 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) the white solid precipitate is filtered and washed with methanol, and then dried to obtain the white solid adsorbent MOF material NUC-200.

[0039] The specific steps of using MOF material NUC-200 to separate carbon dioxide / methane mixture include the following: 1) passing the carbon dioxide / methane mixture into a stainless steel tube adsorption column containing activated MOF material NUC-200, wherein the activation temperature is 90°C when the MOF material NUC-200 is activated, nitrogen is used for 6 hours, the pressure of the carbon dioxide / methane mixture when passing into the adsorption column is 1.01 bar, the flow rate is 1 mL / min, and the indoor temperature is 25°C. At the same time, during the separation process, the flow rate, pressure and indoor temperature of the carbon dioxide / methane mixture remain unchanged. 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 methane; 2) the carbon dioxide adsorbed on the MOF material NUC-200 is collected by vacuum desorption.

[0040] Example 2: Application of a MOF material NUC-200 in the separation of carbon dioxide / nitrogen mixed gas, wherein the preparation method of the MOF material NUC-200 comprises the following steps: 1) zinc acetate and 4,5-dicyanoimidazole are sequentially added to methanol and stirred to dissolve to form a mixed solution; 2) ammonia water is added to the mixed solution and stirred and reacted 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) the white solid precipitate is filtered and washed with methanol, and then dried to obtain the white solid adsorbent MOF material NUC-200.

[0041] The specific steps of separating the carbon dioxide / nitrogen mixture using the MOF material NUC-200 include the following: 1) passing the carbon dioxide / nitrogen mixture into a stainless steel tube adsorption column containing the activated MOF material NUC-200, wherein the activation temperature is 90°C when the MOF material NUC-200 is activated, nitrogen is used for 6 hours, the pressure of the carbon dioxide / nitrogen mixture when passing into the adsorption column is 1.01 bar, the flow rate is 1 mL / min, and the indoor temperature is 25°C. At the same time, during the separation process, the flow rate, pressure and indoor temperature of the carbon dioxide / nitrogen mixture remain unchanged. 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 nitrogen; 2) the carbon dioxide adsorbed on the MOF material NUC-200 is collected by vacuum desorption.

[0042] 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. Application of MOF material NUC-200 in separation of carbon dioxide / methane mixed gas, wherein: The preparation method of MOF material NUC-200 includes the following steps: 1) adding zinc acetate and 4,5-dicyanoimidazole to methanol in sequence and stirring to dissolve to form a mixed solution; 2) adding ammonia water to the mixed solution and stirring and reacting 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 the white solid adsorbent MOF material NUC-200.

2. The use of the MOF material NUC-200 in the separation of carbon dioxide / methane mixed gas according to claim 1, characterized in that: The molar ratio of zinc acetate, 4,5-dicyanoimidazole, methanol and aqueous ammonia is 1:2:0.57:0.

002.

3. The use of the MOF material NUC-200 in the separation of carbon dioxide / methane mixed gas according to claim 2, characterized in that: In step 2), the stirring temperature is 0°C to 40°C, and the stirring time is not less than 18 h.

4. The use of the MOF material NUC-200 in the separation of carbon dioxide / methane mixed gas according to claim 3, characterized in that: The specific steps of separation include: 1) passing carbon dioxide / methane into an adsorption column containing activated MOF material NUC-200, and directly collecting high-purity methane at the outlet; 2) collecting carbon dioxide adsorbed by MOF material NUC-200 by vacuum desorption.

5. The use of the MOF material NUC-200 in the separation of carbon dioxide / methane mixed gas according to claim 4, characterized in that: In the specific step 1) of separation, the pressure of the carbon dioxide / methane mixture when passing into the adsorption column is 1.01 bar, the flow rate is 1 mL / min, and the indoor temperature is 25°C.

6. Application of MOF material NUC-200 in separation of carbon dioxide / nitrogen mixed gas, wherein: The preparation method of MOF material NUC-200 includes the following steps: 1) adding zinc acetate and 4,5-dicyanoimidazole to methanol in sequence and stirring to dissolve to form a mixed solution; 2) adding ammonia water to the mixed solution and stirring and reacting 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 the white solid adsorbent MOF material NUC-200.

7. Use of the MOF material NUC-200 according to claim 6 in separation of carbon dioxide / nitrogen mixed gas, characterized in that: The molar ratio of zinc acetate, 4,5-dicyanoimidazole, methanol and aqueous ammonia is 1:2:0.57:0.

002.

8. Use of the MOF material NUC-200 in separation of carbon dioxide / nitrogen mixed gas according to claim 7, characterized in that: In step 2), the stirring temperature is 0°C to 40°C, and the stirring time is not less than 18 h.

9. Use of the MOF material NUC-200 according to claim 8 in separation of carbon dioxide / nitrogen mixed gas, characterized in that: The specific steps of separation include the following: 1) passing the carbon dioxide / nitrogen mixture into an adsorption column containing the activated MOF material NUC-200, and directly collecting high-purity nitrogen at the outlet; 2) collecting the carbon dioxide adsorbed by the MOF material NUC-200 by vacuum desorption.

10. Use of the MOF material NUC-200 according to claim 9 in separation of carbon dioxide / methane mixed gas, characterized in that: In the specific step 1) of separation, the pressure of the carbon dioxide / nitrogen mixture when passing into the adsorption column is 1.01 bar, the flow rate is 1 mL / min, and the indoor temperature is 25°C.

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